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.
Files with .XLT extension are template files created with Microsoft Excel which is a spreadsheet application which comes as part of Microsoft Office suite. Microsoft Office 97-2003 supported creating new XLT files as well as opening these. The latest version of Excel is still capable of opening these old format template files. Such a template file is used to quickly create new Excel files with default data and settings such as page formatting, font size, margins, charts, etc which can be further saved as new .XLS files.
You can also convert CSV into many other file formats. Please see the complete list below.