Use the noun coverage to talk about how much something is covered or included. If your history book's coverage of the Civil War is skimpy, you might want to do some extra research at the library.
There's the TV news coverage of the winter Olympics — in other words, the way they show and comment on the events — and the spotty coverage of your lawn by the grass you planted. Something is covered in both examples, either literally or figuratively, and it's more common to use coverage in a figurative way. There's also insurance coverage, or the extent of protection it provides: "I have the cheapest car insurance coverage, so it won't pay to fix these dents."