Survivorship (or survival) bias is the error on concentrating only on the things or people that made it through some type of screening process. This unfortunately means overlooking those who did not "make the cut" and can lead to errors and false conclusions in an analysis.
For instance, this can lead to some false conclusions. For example, if several football players in a high school are offered football scholarship one may automatically come to the conclusion that the high school has an exceptional football program. The school may have an excellent program, or if the survivorship bias has occurred it may just only have had a few exceptional players.