Puja is a word in Sanskrit language. Pujas are an ancient form of pleasing Gods. Puja's have different types of meaning they are:
i. 'P' for 'Paapa'(sins), 'J' for 'Janma' (birth), that means 'p' it removes all accumulated sins, and 'j' it makes your life's (birth) purpose fulfilled.
ii. The word "puja" consists of two letters, "pa" + "ja". "Pa" means "Parayana" (continuous repetition of the names of God). "Ja" means "Japa" (continuous mental recitation of the names of God).
iii. Puja => "Pu" + "Ja"; "Pu" means "Pushpam" (flower); "Ja" means "Jal" (Water). In the puja ceremony both flowers and water are offered to the deity during the worship.
Puja is a sacred ceremonial act (reverence to a God through invocation; prayer like mantra, slokas; song; and ritual) of performed on different events to adoration. Puja is a spiritual connection with the divine. The methods are to worship in an object element of nature, water, fire, precious jewel, a sculpture, an idol, an image or other symbol of the god etc. These objects are created as receptacles for spiritual energy to direct communication with divine, which you can touch, feel, smell, see, feel the taste of. Thus all wandering senses are brought to a focus, by belief (faith) and by daily practice.
In Hinduism pooja is the most popular form of divine worship. Poojas are performed either by individuals or by groups and either directly by a worshiper or indirectly by a priest on behalf of the worshiper. Although many people take liberties with it to express their love and devotion to God in their own individual ways, the traditional form of pooja has a definite form and structure built around, which is usually followed in more traditional households, temples and religious places.
There are several poojas to reduce the suffering people due to the unfavorable position of planets, and some specific events also, like starting of a business, or the beginning of a journey etc.
Mantra means "to free from the mind" it is a strange divine formula, which if repeated will ultimately lead to divine consciousness. Mantra is a collection of letters scientifically arranged and energized by constant repetition. They give rise to definite forms; repetition of a Mantra has a mysterious power of bringing about the manifestation of the Divinity. It represents this very Consciousness; it becomes the means of awakening the hidden Consciousness in us. Chanting mantras of auspicious lines or words to overcome the problems, and also the sound patterns also work with different parts of the body and can affect the outcome.