Perhaps this requires some explanation.
There are many ways to dissect a poem, and a lot of words can be used to explain them. I mostly ignore the minutiae of technical analysis of poetry (to some that may be obvious) but the difference between perfect rhymes and slant rhymes bears some looking into. They're the most obvious rhymes to differentiate and the most fun to play around with.
A perfect rhyme is a rhyme where the last vowel and consonant sounds correspond perfectly, such as in the aforementioned "fly/high/sky." Other examples include "head/dead," "visionary/cautionary," and so on.
On the other hand, a slant rhyme is a rhyme where the last vowel sound corresponds (or comes close) but the consonants don't necessarily have to match. These can range from the very similar, such as "art/dark" to the more dissimilar, such as "palm/lung."
Perfect rhymes have their place, but slant rhymes are open to much more possibility. I feel a lot of stress is placed on rhyming things perfectly, especially to people just starting to write poetry, but it's simply not critical.
Give them a try!
Give them a try!
(I was first acquainted with slant rhymes when I started writing down and looking at song lyrics, especially those of Death Cab for Cutie and Radical Face. If you need a further example of what I'm talking about, take a listen to the lyrics for "Winter Is Coming" by Radial Face and "Stable Song" by Death Cab for Cutie.)