Blank verse is simply verse that doesn't rhyme.
I've never understood why, but some people seem to consider it a species of crime.
In his plays William Shakespeare positively throve upon it.
Although I admit things were different when he came to write a sonnet.
I think just maybe that it's
We're taught that poetry fits
With metre and rhyme
That work all the time.
When it doesn't it gets quite dissonant.