What exactly is a “Combo List”, and why is this site providing them for free?

After asking for e-mail lists the other day, I got linked to this: https://combo-list.com/

This is a very strange "blog" which appears to be regularly publishing (or linking to, rather) lists of e-mail addresses which have supposedly been leaked in data breaches. I have no interest in the passwords, but it seems to also include those. I’m not sure if those are really the passwords to the e-mail accounts, or passwords for something else entirely.

My interest in this has nothing to do with using somebody else’s e-mail account.

They don’t mention what a "combo list" is, and I cannot figure this out from searching or thinking. It seems like the blog assumes that everyone knows what it is.

I also thought it was a fake site at first, but eventually did manage to download a list, and it appears real. But then again, who knows what kind of information really is in those lists?

I basically wonder why anyone would run such a site, and regularly update it. Why would they give out this info to the public like this? What’s in it for them? Why would they want more spammers to send e-mails to these victims of data breaches?