What happens if you skip the practice games?

I haven't played any league games yet in StarCraft 2. When I go to the league page, there is a button that suggests something like "test skills". As far as I know it will be 5 games to determine my level and to put me in the most appropriate group (bronze, silver, etc).

But there is also "Skip" button. What will be if I skip those testing? Will I be able to play few games and than go back to tests? Or I will be put into "Bronze" league instead?

You start out in the practice league. In this league you play unranked matches against other practice league players, on special maps designed to prevent early rushes. Matches in the practice league also take place at a slower game speed.

You can play 50 games in the practice league before you have to move on. You can also choose to leave the practice league early, but if you do so you won't be able to go back. (This is the "Skip" button you mentioned)

Once you leave the practice league, you begin a series of 1v1 placement matches to determine which 1v1 league you will be placed in (Bronze, Silver, Gold, etc.) You can't play any ranked games (1v1, 2v2, etc) until you leave the practice league.

I believe this "test skills" option you are referring to is your practice games. You get 50 practice games, and they are optional. These games don't count for anything in your profile. I'm not sure exactly whom they are against (whether other practice league players or regular league players).

Once you run out of your 50 practice games (or skip them), you will not be able to go back.

After the practice games, you will then be put into your placement matches. From this point on, your games record goes into your profile. The placement matches are to determine in what league you will best be placed (Bronze, Silver, etc.). Once your placement matches are over, you will be in one of those leagues. You won't be able to choose to go back to the placement matches again - the matchmaking system will only be matching you up against people it thinks are evenly matched with you.

Personally, I skipped the practice games. I wanted to start playing against people the system thinks are evenly matched with me as soon as possible.