Question

What is peer review?...

Answer 1

It's the system of real scientists telling each other what they're working on
and what they're discovering.

When one scientist or team of scientific researchers finds something,
they write a report to let everybody in the world know about it.  But even
before it gets published, they pass it around to their 'peers' ... other
scientists who know a lot about the same subject and may be working
on the same thing. 

The main job of the peers is to try to find mistakes ... either in how the
experiment was done, or in how the report is written.  When the peers
have all done everything they can to pull it apart, maybe the report gets
re-written before it's published, or maybe it never gets published at all,
because the peers found that the experiment didn't really come out the
way the original researchers thought it did. 

This is why I get so burned up when I see a comment on a YouTube
video where the commenter says that a scientist's work is defective.
He's trying to say that the scientist who did all the work, AND all of
his peers who reviewed the report before it ever went out, are all wrong.
This is a group of people who, all together, know everything there is to
know about the subject, and this internet troll, who just watched a 5-minute
video and hasn't even read the full report on the work, and would never
understand it if he did, he comes and says they're all wrong.
That really grinds my gears.

Answer 2

computing or networking is a distributed application architecture that partitions tasks or work loads between peers. Peers are equally privileged, equipotent participants in the application. They are said to form a peer-to-peer network of nodes.