Source protection is when someone wants to tell you a secret or give you some information, but they do not want anyone else to know that they were the one who told you. Like when you tell mommy that you spilled your juice on the carpet but you do not want daddy to know that it was you who did it.
Source protection is important because sometimes people have important information that they want to share, but they may be afraid of getting into trouble or being hurt if they tell anyone. So, they need to trust that you will not tell anyone else where you got that information from.
To protect their identity, you need to keep their name and the details of where you got the information from a secret. You can do this by not telling anyone else about it or keeping it safe by only telling people who need to know.
Just like mommy promises not to tell daddy about your spilled juice, professionals like journalists and lawyers promise to protect their sources and keep their identities a secret. This helps people feel more comfortable sharing important information without worrying that they will get hurt or punished for speaking up.