Use of child

Ok, this is another part of VB I have never used, but feel I should know the purpose of incase I need it at a later date.

I have just downloaded a sample project using the parent & child forms, this is the first time that I have seen someone use them. Can anyone explain why these are in vb please, & why I would use these rather than normal forms?

Thank you :D

If you want to make a program that handles many files at the same time, it's good to use MDI forms and child forms.