Go to Cell A2. Cell A2 is highlighted. Notice that when you are in the cell, its information appears not only in the cell itself but also on a display at the top of your screen just below the menu bar. But it appears in a slightly different way. Now go to Cell B1.
Spreadsheets handle text and numerical data differently.
As far as the program is concerned, the only difference is in the mathematical functions that it can perform using numeric data. The apostrophe is used, in part, to distinguish between the two. The program doesn't show the apostrophe in the cell, but does register the data as text rather than numeric. Go to Cell B1. Cell B1 is highlighted.