Question about combolists

Hello everyone.
I bought a hacking program, and there is a combolist maker inside.
It requires me to upload a passwordlist and fill in the (for example) IG username.
After that, I get a txt file with the username:password structure.

This is the part I totally understand.

But when I download email:pass combolist (on this forum for instance)
Its a text file with a lot of random emails and random passwords.
Are those passwords connected to the emails?
If I put that in a crackingtool, what does it exactly do?

Thanks in advance