Concatenate is a function in excel that allows you to merge together cells. This saves you time in not needing to retype the contents of two cells into one.
See how you can choose many cells to merge, if you wanted to. And to the right of the screen, you can see the result of the merged cells. So in the example BMWRed.
The purpose of this function is to allow user to easily combine data. For example, merging a first name with a surname, or adding a prefix or suffix to a string of data.