Question

How are chromatin , chromatid and chromosomes related?

Answer 1

these are related in such way that all of these are parts of nucleus in any way and are heredity materials

Answer 2

chromosomes are the things you inherited from your parents. 23 pairs. 46 total. (like 23 pairs of socks) 
chromatids are the individual chromosomes in a pair (so like having two red socks, two blue socks. one red sock is a sister chromatid to the other red sock, and same with the two blue socks.)
chromatin is the strands of DNA combined with proteins that make up the chromosome (the thread used to make the socks)