Microsoft Excel is the most widely used spreadsheet application and, with its interfaces, offers an enormous range of possibilities for everyday data tasks.

What makes Excel so special?

First and foremost, it is used by many people worldwide, making the file format of Excel spreadsheets very suitable for collaboration. 
The features have been continuously developed since the first version in 1985, and the existing developments have practically become a standard.
If you use this application including the programmability, database and add-ons, you can travel from the world of spreadsheets to the universe of spreadsheets.
The file format was originally .xls, but in 2007 it then became Excel Spreadsheet .xlsx and Excel Spreadsheet with macros .xlsm.
The original formats .xls, xla (Excel Add-ins), .xlt (Excel templates) are still usable today. 
Of course there is no light without shadow; some automatic functions can initially almost annoy the user when data are converted into a date, but there are simple workarounds that prevent this "unwanted" help from Excel.

Alternatives to Excel are the spreadsheet applications from Apache: OpenOffice Calc, LibreOffice Calc; here you will find similar functions that are almost compatible, but only almost, so exchanging spreadsheets and collaboration is not recommended; even though these alternatives are free and really good on their own.