You would use the For Each…Next loop to perform an action on every cell in a range of data. Suppose, for example, that you wanted to make the word "OK" darker than other text everywhere in a selected range. Your code would look like this:
"MyCell" means whatever cell the loop is working on, and "For Each" means that the loop will work on all cells in the selection. If the loop finds a cell containing only the word "OK", then it makes that word darker. (The appearance of text is controlled by the Font property, and the Bold property means darker text.)