Is there any difference in meaning or usage of this two words? In case, what is it?
der Berg and das Gebirge
They both mean "mountain".
There is also a plural of Berg (Berge), but there is a difference to Gebirge. Berge is a list of mountains, Gebirge is an area with mountains.
You find also some defintions in the Wikipedia article for Gebirge
Also, to complicate matters further, there is another meaning of Gebirge in the field of mining (Bergbau, i.e. mountain de/construction). There, Gebirge means the underground rock, especially if it has not yet been mined. This includes loose rock like sand
berg~ seems to be a rather versatile root:
bergen, geborgen, verbergen, Berg, Gebirge,…