what's freemanverse?

you know that gordon freeman guy? the silent protagonist from classic fps half-life? well it's that guy... multiplied by, like... ten.
freemanverse/gordonverse/freeverse/gverse is just different variations of gordon hanging out... like spiderverse. or sans.
i looove freemanverse! but it's also difficult to get into... and everyone only ever talks about the main four...
so in order to demystify freemanverse (and catalogue my own headcanons), i made a little... wiki database thing!