Picom

Picom is a lightweight standalone compositor created for the X Window System. It is a fork of compton, created because compton wasn't being actively maintained; compton is, in turn, a fork of xcompmgr-dana, forked from xcompmgr.

Configuration
Picom can be configured using a config file which in most systems is located at. However, picom can also be made to start with a custom config file using the following options:

Usages
picom has multiple configurations in which it can be run, however in most instances when using it in conjunction with another window manager the  flag is used to start it as a background process.