Spreadsheet Files Extensions - What are spreadsheet files and how do I open a spreadsheet file?

What are spreadsheet files and how do I open a spreadsheet file?

File Type Category File Format
.ast Spreadsheet Files Ability Spreadsheet Template
.gsheet Spreadsheet Files Google Drive Spreadsheet
.nmbtemplate Spreadsheet Files Numbers Spreadsheet Template
.ods Spreadsheet Files OpenDocument Spreadsheet
.ots Spreadsheet Files OpenDocument Spreadsheet Template
.sdc Spreadsheet Files OpenOffice.org Calc Spreadsheet
.wq1 Spreadsheet Files Quattro Pro for DOS Spreadsheet File
.xls Spreadsheet Files Excel Spreadsheet
.xlsm Spreadsheet Files Excel Open XML Macro-Enabled Spreadsheet
.xlsx Spreadsheet Files Microsoft Excel Open XML Spreadsheet