Files with CSV (Comma Separated Values) extension represent plain text files that contain records of data with comma separated values. Each line in a CSV file is a new record from the set of records contained in the file. Such files are generated when data transfer is intended from one storage system to another. Since all applications can recognize records separated by comma, import of such data files to database is done very conveniently.
Text files created with Markdown language dialects is saved with .MD or .MARKDOWN file extension. MD files are saved in plain text format that uses Markdown language which also includes inline text symbols, defining how a text can be formatted such as indentations, table formatting, fonts, and headers. MD files can be converted to HTML with a program called Markdown. Markdown language is released by John Gruber.
You can also convert CSV into many other file formats. Please see the complete list below.