Minifies CSS/JS files which are passed through the assetbuilder in CiviCRM.
For example if it is installed on a CiviCRM system it will minify crm-menubar.css. If Stripe is installed it will minify stripe css/js.
Releases
Since CiviCRM 5.x, extension releases compatible with CiviCRM 5.0 are compatible with 5.0 and later. An extension release compatible with 5.25, for example, means that it requires CiviCRM 5.25 or later.