Plugins are used to extend the functionality of nopCommerce. nopCommerce has several types of plugins.
For example, payment methods (such as PayPal), tax providers, shipping method computation methods (such as UPS, USP, FedEx), widgets (such as 'live chat' block), and many others. nopCommerce is already distributed with many different plugins.
You can also search various plugins on the nopCommerce official site to see if someone has already created a plugin that suits your needs.
If not, this article will guide you through the process of creating your own plugin.
The plugin structure, required files, and locations.
First thing you need to do is to create a new "Class Library" project in the solution.
It's a good practice to place all plugins into \Plugins directory in the root of your solution (do not mix up with \Plugins subdirectory located in \Nop.Web directory which is used for already deployed plugins).
It's a good practice to place all plugins into "Plugins" solution folder (you can find more information about solution folders here).