Pure pure or impure rhyme?

Hi, I googled but I couldn't find a suitable answer to my question… How do I recognize an impure rhyme? and how do I recognize a pure one? I half understand impure rhymes. The consonants/vowels sound similar. Do the consonants/vowels have to sound the same in pure rhymes? I got that from the ballad John…

Poem/ballad?

So, at school we were given the task of learning a ballad in two weeks. The choices are: "The Sorcerer's Apprentice," "John Maynard," and "The Glove." I can't seem to decide. I don't really like "The Glove," "The Sorcerer's Apprentice" rhymes well, but it's the longest of the three, and "John Maynard," I don't know….