Okay kiddo, so you know how sometimes people work on projects together, like building a Lego tower? They might split up the work and each work on different parts of the tower.
Well, sometimes people work on computer programs and need to do the same thing. TortoiseBZR is a tool that helps people work on computer programs together. It's kind of like a big Lego tower, and each person has their own special blocks that they're responsible for.
TortoiseBZR works by keeping track of all the changes that each person makes to their part of the program. That way, if someone accidentally messes something up, they can go back and fix it easily.
It also helps everyone see the same version of the program, so everyone is always working with the most up-to-date version. It's like everyone has their own Lego tower, but when they're done, they put all the pieces together to make one big tower.
Basically, TortoiseBZR is like a helpful tool that makes it easier for people to work together on computer programs.