MySQL default table type is MyISAM, where there are three kind of files that are stored inside MyISAM. The file names begin with the table name and have the extensions such as frm, myd and myi. The explaination of each file is given below:
.frm file consists of the table definition that are stored in the database
.myd is an extension that is used by a data file.
.myi is an extension that is used by index file.