Use comparable to describe two things that are alike. If you are offered two jobs with comparable salaries, you might take the one where the weather is nicer.
Comparable can also mean exactly what it looks like: things you are “able” to “compare” are comparable. When you say that comparing two things is “like comparing apples and oranges,” you're saying the two things in question are not comparable. When you pronounce this word, remember that, unlike with “compare,” you emphasize the first syllable and swallow the first “a”: COM-pra-ble. The sounds of the two words aren't really comparable.