Worship or prayer or puja in hindi can be properly classified as Stuti, Prarthana (Yachna), Samarpan (Ishwar Pranidhaan) and Upasana. Now lets go through these in brief:
Stuti - can be described as remembering the attributes of God and reforming one's character as per the God's attribute by falling in love with those attributes. This does not mean that you say "God can do everything as he is omnipotent". This sentence would be of error as God can not be devoid of knowledge or die etc. The right way of Stuti would be to say that God does not need any help in his work like creation of the worlds etc. God's attributes can be Glorified as Positive as well as Negative as described below.
Prarthna - Can be described as we asking God for internal courage to do Purshartha (karma or work) for enhancing our happiness. For example asking for the divine help in practicing Satya in our behaviour, communication etc. In other words, the request for Nishrayas (Atmik pleasure or pleasure for the Soul) like knowledge, concentration, purity etc. is called Prarthna.
Yachna - can be described as we asking (precisely begging) God the things for our happiness (e.g. house, wealth, children etc). A Yachak (person who is asking) can only ask for things from the lord or the possessor of those things. When you are doing Yachna, it generates a feeling in you that some entity is greater than you. The request for the Abhudaya (material pleasures) like food, clothes, wealth etc. is called Yachna.
The words Prarthana and Yachna are similar yet different. Similarly, Samarpan and Ishwar pranidhaan are closely related words.
Samarpan - is to completely (in mind, work & voice) surrender yourself to the Almighty. Maharishi Patanjali explains in Yoga Darshan that when a human realises that the body, intellect, thinking capability, senses, material possessions etc. have been given to him / her by the grace of the Almighty then that person completely surrenders himself / herself to the God. Similarly, Shri Krishna advises Arjun in Gita (9/27) that " O son of Kunti! whatever work you are doing, whatever you are eating, whatever oblations you are giving in the Yajna, whatever donation you are giving, whatever you are praying, offer it all to me (etymologically meaning the Omni present Lord)".
Ishwar Pranidhaan - is surrendering all the work done by an individual to God. When an individual starts working with the feeling that whatever he/she is doing is inspired by the ever present God in his/her heart then the feelings of prejudice, selfishness and greed starts diminishing from that individual.
Upasana - Upasana literally means to sit near the Almighty. To elaborate more
Worship in simple is the glorification of Godís attributes. Glorification gives rise to love of the Supreme Being, reformation of oneís nature, character and attributes in accordance with the nature, attributes and character of God. Prayer creates humility, courage and obtains divine help. Prayer does not mean that He will suspend His Laws and forgive the sins of his devotees. Many people preach that by joining their religion all your sins will be forgiven. In a way they encourage people to sin because according to them by taking Godís name or chanting few mantras or drinking holy water they can be rid of their sins and can keep on repeating the procedure to purify them. They fail to realise that He is not a person like us who can change his laws for his devotees who sing His praises and bribe Him by offering sacrifice as many scriptures inculcate. He is known as the Supreme judge and His laws are unchangeable. Everyone is the same in His view and He is definitely not prejudiced.
Glorification can be of two types:
Positive Glorification: Positive Glorification consists in praising God as possessed of positive attributes as per example below -
"That Supreme being overspreads all. He is entirely spirit, All-energy, All powerful, Pure, Perfect, Omniscient, Inward Controller of all, Ruler of all, Eternal and self existent. He has from all eternity been teaching uncreated immortal human souls, the true knowledge of things through the revelation of the Veda - His eternal knowledge." ... Yajur Veda XXXX,8.
Negative Glorification: Negative Glorification consists in praising God as devoid of such ungodly qualities as passion and malice in the following way -
"He is never embodied, is never born, is never liable to division and is free from nervous or arterial systems, never commits a sin, is never subject to pain, grief and ignorance and the like." ... Yajur Veda XXXX,8.
The object of Glorification is to reform one's nature, attributes and character after the nature, attributes and character of God, for instance let him be just as God is and so on. He who praises God like a flunkey, but does not reform his character does himself no good.
Q: If God does not pardon our sins then what is the use of Upasana?
A: Upasana is done to reform oneís nature, attributes & character as per the positive glorification or rid oneís nature, attributes and character of all bad qualities as per negative glorification. Upasana also gives atmik shakti (internal strength), which is helpful in overcoming the internal enemies like lust, avarice, etc. and achieving true happiness.
If the sins are pardoned by Upasana then it will encourage hardened criminals and others to commit crime as all they have to do is to sin and ask God for pardon. There will be nothing to motivate the reform of humans without Upasana.
Q: Donít you think a person gets happy by acquiring wealth?
A: Yes, a person does get happy momentarily by acquiring wealth. But this happiness is short lived as that person is still vulnerable to sadness, ill health, fear of loosing the wealth etc. However, if a person has learnt to control his senses and mind through yoga and is cognisant of God is rid of worries, sadness, depression irrespective of bodily pain or ill health etc. and achieves happiness by the grace of the almighty.
Maharishi Dayanand in his Rig Ved Adi Bhashya Bhumika (Athopasana Vishay Sankshept) explains the quality of a yogi as per Yajurved 11/2 as below:
ďYog ko karne wale manushya tattva arthath Bramhajnan ke liye jab apne man ko phailay Parmeshwar me yukt karte hai, tab Parmeshwar unki buddhi ko apni kripa se apne me ukath kar leta hai. Phir ve parmeshwar ke prakash ko nischay karke yathawat dhaaran karte hai. Prithvi ke beech me yogi ka yahi prasidh lakshan hai.Ē
When the persons practising Yoga establishes their mind in God then God favours them by establishing their intellect in him. That is when they become cognisant with the Godly light and wear it in their life. This is the famous quality of a yogi on our earth.