so this could be a very noob question , but here it comes :
i have seen in many games that the people talks about “props”,as game objects whats that exactly?
Props are anything tangible that the characters may interact with. Say, for example, a beach ball that the character can go ahead and randomly kick into a neighbors window.
Yeah it’s a theatrical term from way back, before movies even. It’s short for “property”.
-LP
It’s a term from theater.
From wikipedia:
“…an object used on stage by actors to further the plot or story line of a theatrical production. Smaller props are referred to as “hand props”. Larger props may also be set decoration, such as a chair or table. The difference between a set decoration and a prop is use. If the item is not touched by a performer for any reason it is simply a set decoration. If it is touched by the actor in accordance to script requirements or as deemed by the director, it is a prop”.
Basically an object intended for actor interaction. 
Props are the objects which are used by the performer in any play. If any performer is given with any prop then he/she has to completely stick to it or he / she has to use it throughout hi/her act. Anything like stick, ball, ring, etc could be a prop.
Static meshes- map models that are stationary but have bounding or clipping.
Physics meshes- map models that can be moved and or interacted with. <-----props.
I kinda thought it meant almost everything, trees, rocks, houses, etc. Guess it wasn’t such a noob question after all, unless I’m a noob…
…nvm, no going there.
Learned something new :D.
There’s still some gray area though; like the hats in TF2 and the accessories in Portal 2…