Sacrificial lamb

Okay, imagine you and your friends are playing a game of tag. But you notice that one of your friends is really slow and keeps getting tagged first every time. So you decide to be a good friend and take one for the team. You offer yourself up as a "sacrificial lamb" and let yourself get tagged first, so your slower friend has a better chance of not being "it" and getting a turn to chase everyone else.

In real life, a "sacrificial lamb" is someone who takes the blame or punishment for something that other people have done. They might not have done anything wrong themselves, but they are willing to suffer the consequences in order to protect someone else or to make the situation better for everyone. It's like being the first one to take a hit, so that others can avoid getting hurt.