Final answer:
Homologous chromosomes are pairs of chromosomes with the same genes, while sister chromatids are identical copies of a chromosome bound to each other. They are both involved in DNA replication and cell division.
Step-by-step explanation:
Homologous chromosomes are pairs of chromosomes that have the same genes in the same order, although they may have different alleles. They are similar in size, shape, and genetic content, and are derived from different parents. On the other hand, sister chromatids are identical copies of a chromosome that are produced during DNA replication and are physically bound to each other at the centromere. In humans, each homologous pair of chromosomes is also bound to an identical sister chromatid, resulting in the familiar 'X' shape.