Plugin:
nearly 30 different standard types of plugins and even more sub-plugin types, however all of these plugin types work the same way.
Blocks and activities are the only small exceptions.

Although there are many different types of plugin, there are some things that work the same way in all plugin types. Please 

Naming Conventions:
Plugins typically have at least two names:

    The friendly name, shown to users, and
    A machine name used internally.

The machine name must meet the following rules:

    It must start with a lowercase latin letter
    It may contain only lowercase latin letters, numbers, and underscores
    It must end with a lowercase latin letter, or a number
    The hyphen, and minus character - are not allowed


Moodle
Moodle is a powerful, and very extensible, Learning Management System. One of its core tenets is its extensibility,
and this is primarily achieved through the development of plugins.