A skewer is almost like a pin, but this time the king will be protecting the queen for example:
As you can see the king has to move to a different square and then the bishop on f4 can take the queen. In the pin blog, the queen is not able to move, but skewer is when the king goes to another square where there is a piece behind it which could be a bishop, rook, knight, and a queen (PAWNS DO NO COUNT AS A SKWEWR). Skewers do not happen much often because they are very easy to find. Skewer is dangerous when it occurs. Don't worry you could identify if you get a skewer or not (VERY EASILY). If you do get in a situation where you in a skewer then try to look for any other counter plays. If not then at least try to fight back your piece or draw the game.