What is a Puja?
I generally translate puja to mean a devotional service. But based on a query in my previous post, Pratik provided a beautiful and succinct explanation. Considering no single word or phrase comes even close to incorporating this meaning, I recommend not translating it, but using the word puja as is, in the english language. Interestingly, this meaning is not unique to Hinduism (or Sanatana Dharma) and applies to all religious beliefs.
Pu comes from the word Poorna in Sanskrit meaning complete, Ja comes from Aja meaning born. So Puja is that which is born out of completeness or fullness.
It signifies that you feel complete and happy, and you are grateful to the Divine for bestowing that completeness in life. In fact the offering that we give symbolizes all the good things bestowed upon us by the Divine. It (is) like we are imitating the Divine in gratitude.