Think of a spreadsheet as a huge sheet of graph paper. The columns run down the sheet and are labelled with letters — A, B, C, and so on. The rows run across and are labelled with numbers — 1, 2, 3, and so on. Every little box where a column meets a row is a cell, and it is the place where you actually type your data.
The moment you have a grid like this, you need a way to point at any one box and say "this one." That pointing name is the cell address.
Cell address
A cell address is simply the column letter followed by the row number, written with no space between them. The cell sitting in column B and row 5 is called B5. The cell in column A, row 1 is A1. The letter always comes first, the number second — never the other way round.
Why this order? Because it mirrors how you'd give directions on the sheet: first go across to the right column, then go down to the right row. The letter fixes your horizontal position, the number fixes your vertical position, and together they pin down exactly one cell. That uniqueness is the whole point — no two cells can share an address, and one address can never mean two cells.
The column letter is written in capitals by convention, but spreadsheets treat b5 and B5 as the same cell. The address is a label, not a calculation.
Cell range
Often you don't want one cell — you want a whole block of them, say all the marks from row 1 to row 10 in column A. Instead of listing A1, A2, A3 … you describe the block by its two opposite corners: the top-left cell and the bottom-right cell, separated by a colon.
So A1:A10 means "the rectangular block starting at A1 and ending at A10." The colon is read as "through" or "to." For a block that spans several columns and rows, like B2 to D6, you write B2:D6 — again top-left first, bottom-right second.
The two corners you name must be diagonally opposite, so that together they define a rectangle. A1:A10 is a single column of ten cells. A1:C1 is a single row of three cells. A1:C10 is a full rectangle, three columns wide and ten rows tall. …