What is the purpose of the following files having extensions 1) .frm 2) .myd 3) .myi? What do these files contain?

In MySql, the default table type is MyISAM.
Each MyISAM table is stored on disk in three files. The files have names
that begin with the table name and have an extension to indicate the
file type.
The ‘.frm’ file stores the table definition.
The data file has a ‘.MYD’ (MYData) extension.
The index file has a ‘.MYI’ (MYIndex) extension,