-- An active cell, also referred to as cell pointer is the currently selected cell in a spreadsheet. It is the selected cell in which data is entered when you begin typing. It can be identified by a bold (typically blue) outline that surrounds the cell.

-- Whenever you click on a specific cell within a spreadsheet, it becomes the active cell. When an action takes place in the spreadsheet - such as data entry, formatting, or deleting data - it is the active cell that is affected.

-- For example, data can only be entered into a worksheet one cell at a time and the active cell is the place where that data will be located.

--It helps identify what cell is being working with and where data will be entered.

Active cell is the where the pointer remains or the cell is which highlighted (by a thick black border).

How do you know one? Try typing and the the cell which displays the output will definitely be the active cell.

Other than identification of where you are in a spreadsheet there is no other utility.

In excel Active cell is nothing but the Cell which is currently in use.