– Excel is a spreadsheet application that is a part of Microsoft Office 365.
Some people use only one or the other. Other people use both.
If a Google user who does not have Excel installed receives an Excel spreadsheet via email, the user can preview the spreadsheet within Gmail and then convert the spreadsheet to Google Sheets.
There are several ways to move spreadsheets and spreadsheet data between Google Sheets and Microsoft Excel. Here are examples of Google Excel information exchange.