I am sure that by now you realize that chess is game of give and take. Depending on the game situation you may be more inclined to sacrifice pieces and in other situations you may fight very hard to keep all of your pieces. However, there are a number of chess openings that are referred to as a gambit. The word gambit stems from the Italian 'gambetta' which means to set a trap. The term gambit was also used by Italians to describe a wrestling move. In chess a gambit is simply sacrificing a piece to achieve a better position on the board.
Typically in a gambit it is a pawn that is sacrificed, but there are times where perhaps a bishop or knight is the piece that is sacrificed in the gambit. The idea is that the player who sacrifices something gains something in the process such as time or active piece play. Let's look at the Danish gambit as an example. In this white loses two pawns, but is able to place bishops at an advantage looking to your opponent's kingside.
There are numerous gambits that have been proven and tested time and again. Some of these gambits are more effective than others. An opponent may or may not choose to accept the gambit that you are offering. Your opponent may be familiar with the gambit and elect not to take your sacrificial pieces to keep you from having an advantage. It is up to you to decide if it is in your best interest to use a gambit or to accept a gambit during a game. It would be wise to research many of these gambits and to become familiar with using them in games. There are numerous Internet sites that describe gambits in detail as well as a variety of books on the topic of gambits.