What is the difference between typosquatting and a homoglyph attack?

Typosquatting is the umbrella term. A homoglyph attack is one family under that umbrella — specifically, substituting a character with one that looks visually identical or near-identical (e.g., Cyrillic ‘а’ for Latin ‘a’, digit ‘1’ for lowercase ‘l’, or zero for uppercase ‘O’). When homoglyphs cross scripts (Latin ↔ Cyrillic ↔ Greek), the attack is called an IDN homograph attack and is encoded on the wire as punycode.