Question about Season Pass

Depends on game.

It's an all-in-one package of all the upcoming cut content which is sold separately.

if the game have 5 dlc. and i buy the season pass. am i getting all the 5 dlc for free?

If you have a game and want to get all( or most of the DLCs) you can buy a season pass which is cheaper than buying all the DLCs separately, plus you get access to DLCs that are released in the future. It all depends on the game, read the description of the season pass and it should tell you what you'll get from it.

You buy it and get every dlc that's supposed to be included in it. It depends on the game however. For example with Bioshock infinite you get every available dlc but with Borderlands 2 you get only the 4 biggish campaign dlcs and no costumes or headhunter dlcs. Just read what the description for the season pass says, it usually lists all the stuff that's included in it.