Say that you want book sales under 15 copies to be formatted in bold red to really make underachieving sales stand out. It's probably easy for you to spot the sale under 15 in the picture, but imagine that there are lots of other rows, in which case other under-15 entries could get lost in the rest of the data.
You'd start by selecting column C (which contains the book sales numbers), and then clicking Conditional Formatting on the Format menu.
