This page lists the features. Keep reading and it will cover searching and much more.
This covers the Markdown Joplin uses. Keep reading and you will also see what extensions to Markdown are available (Tools > Options > Markdown). Many of the features listed also have links to more detailed information.
https://joplinapp.org/markdown/
This gives some info on the plugin system
https://joplinapp.org/plugins/
This gives a summary of the available plugins