I dont think its a word as such, they are particles. They are used in japanese as a main part of grammar. Putting them after or before something defines what the words are, ie subject verb object etc.
Quickly;
---ga subject
---de at/with (place de - at 'place', hashi de - by using chopsticks)
---ni at/to (1ji ni - at 1 oclock, place ni - to 'place', boku ni - to me)
---(ha)wa main subject
---(h)e at
some other useful ones are
no - possesive marker, like 'watashi no' means mine. 'anata no' yours etc
(w)o - subject that an action is done to, like to eat pizza would be pizza wo taberu