It is because it is a electronic spreadsheet program. A spreadsheet in the traditional sense is a piece of paper with rows and columns that people use to write figures on and do calculations. In 1978 a business student named Dan Bricklin, thought that there should be a simpler way of doing them than on paper, as they were slow and tedious to use, especially when changes in the figures needed to be made. He got together with Bob Frankston who was a friend and a programmer. They created VisiCalc, the first electronic spreadsheet program. Many other spreadsheet programs were created by other people after that and Microsoft Excel is one of those.
Generally it would still be called a spreadsheet, but it could be called a What-if spreadsheet.
The area of the screen where you interact with a spreadsheet is called the spreadsheet workspace or spreadsheet view. It is where you input, view, and manipulate data within the cells of the spreadsheet.
A spreadsheet is sometimes called a worksheet.
It is called a spreadsheet or a worksheet.
It usually is called a spreadsheet. Microsoft Excel calls it a worksheet.
In a spreadsheet a built-in formula is called a function.
One location on a spreadsheet is called a "cell".
It can be called a worksheet. There is a range of actual spreadsheet programs, so people often refer to them directly, like Excel or Quattro or Works or Open Office or Lotus 123, instead of using the term spreadsheet.
They can be called records, but that is more the case in a database than in a spreadsheet.
It can be called editing.
In Excel it is called a workbook.
The spreadsheet included with the iWork software suite is called Numbers.