Question

A poems rhyme scheme is usually marked with

Answer 1

It is usually marked by letters. Such as ababbcc. That shows what lines rhyme with other lines. There's also AABB, ABAB (shwing that line a rhymes with line a, then line b rhymes with line b. It goes line a, line be, line a, line b.
~Silver

Answer 2

Rhyme scheme. the pattern of rhymes used in a poem, usually marked by letters to symbolize correspondences, as rhyme royal, ababbcc.