what is the definition of logo infringement?

When someone uses a company's logo for their own personal or business purpose without the agreement of the owner of the logo.

For instance, if you took Microsoft's logo and put it on T-shirts for a school play, and sold it, it's logo infringement because you didn't get a written permission from Microsoft.

There are pretty strict fines for it if you use it for business purposes. Personal purposes would make the punishment a little more lenient, but it's still not good.