What does SetHandler "proxy:unix:..." do?

Question

What does the Apache "proxy:unix:..." handler do, and where is it documented? I see it used here and there, like:

SetHandler "proxy:unix:..." 

For example in this recent question, or in the SetHandler and mod_fcgi documentation.

I can guess that it might pipe to a Unix socket, but what about the syntax in the mod_fcgi example? Where's the documentation?

Answer 1

I finally found the answer in the docs for ProxyPass:

In 2.4.7 and later, support for using a Unix Domain Socket is available by using a target which prepends unix:/path/lis.sock|. For example, to proxy HTTP and target the UDS at /home/www.socket, you would use unix:/home/www.socket|http://localhost/whatever/.

Answer 2

This is the sethandler directive documentation:

This describes the use of Apache's handlers