An extension is a piece of code written in C or C++ which will be included into the PHP core when PHP starts. Normally, you have some more native functions available after including an extension. PHP ...
PS: the pre-installed PHP extensions are excluded from this list. You can list them with the following command (change php:7.2-cli to reflect the PHP version you are ...
Package maintainers need to provide pre-compiled binaries for different platforms and PHP versions. These pre-compiled binary files need to be saved in a certain location, currently GitHub seems to be ...