ftplugin is the Vim editor's mechanism for running a set of commands based on the filetype of the file being edited (for instance, html, C, javascript, etc).
A file type plugin (ftplugin) is a script that is run automatically when Vim detects the type of file when the file is created or opened. The type can be detected from the file name (for example, file sample.c has file type c), or from the file contents.
