These are commands that e.g. the Bitcoin CLI client can make to the server.
The commands can be listed with:and full help with:
bitcoin-core.cli help
bitcoin-core.cli help getrawtransaction
For example. to run the Bitcoin and then on another shell:
getrawtransaction
command, first in one shell we start bitcoind:bitcoin-core.daemon
bitcoin-core.cli getrawtransaction 75b431e0a8c4617ca8adefe593ba66aa30907742b6dc8772761bfe7edabd74b4 true