What is the meaning of rhyme sheme?

If you really mean "rhyme Scheme" than the answer is a series of lines that follow a particular pattern, usually represented by the letters of the alphabet, such as:

AA, BB,A or A,B,C,A,B,C etc.

An example would be a Limerick, such as:

There once was a fellow from York (A)

who ate all of his food with a fork. (A)

He ate chicken and beans (B)

and meat, by all means (B)

but his friends classed him as a dork. (A)