Systems vs Lines: Building a Repertoire

Two philosophies for opening study (straight from FM Morefield's curriculum):

• A SYSTEM: one setup you play against almost anything — same pawn shape, same piece squares every game. Examples: the London System for White, the King's Indian setup for Black. Cheap to learn, but your games can start feeling identical.

• LINES: a specific prepared answer to each thing your opponent plays. More precise, more powerful — and much more homework.