Context free languages can be more complex than regular languages. Instead of matching simple patterns, they have tree-like grammatical structure,
Grammars, Derivations, and Parse Trees
Fruit flies like a banana: ambiguity is the enemy of grammar.
Ambiguous Grammars, Disambiguation, and Inherent Ambiguity
Parsers turn strings into trees (or error messages if there are syntax errors)
CFL goes beyond REG (a little bit)
Properties of Context Free Languages
And now the bad news: