The ± symbol has the meaning Plus minus sign. It belongs to the category Mathematical Symbols. It is also known as Plus and Minus. The minus sign is located directly below the plus sign. But when do you use the Plus minus sign? If you want to indicate that a mathematical expression can be both positive and negative, then you can use the ± symbol.
Here is a small example: x² = 4
For the variable x, you could now use ± 2.
But also in technology, the Plus minus symbol is used to indicate, for example, the uncertainty or the tolerance. Unfortunately there is no simple Plus minus key combination. You can just copy the ± symbol below.