As just mentioned, a label is a chunk of alphanumeric text. The main differentiating characteristic of a label is that the label isn't used in calculations. Typically, you use labels to describe the values you do want to use in calculations.
As a practical matter, you can enter labels that are as long as you need. But if you type in a label that's wider than the column you're placing it in, you'll often need to adjust the column width. Here's the reason: Although Excel will let a long label spill over into the adjacent cell or cells if they are empty, it displays only the portion of the label that fits in its own cell if the adjacent cell or cells store data.
When a label's display does get cut off because it can't spill over into adjacent cells or you don't want a label spilling over into adjacent cells, you just need to adjust the column width. There are a couple of quick ways to do this. If you want to make a column as wide as the widest piece of data it holds—a label or a value—you can double-click the right border of the column heading button. Alternatively, you can drag the right border of the column heading button using the mouse.