Other forms: lits; litai
If something's lit, it's illuminated with light from a lamp or other source. Your romantic dinner table might be lit only with flickering candles.
A well-lit room provides enough light for whatever task you need to to there — your kitchen might be lit with under-cabinet lights that shine on the counters, and your office might be lit with a desk lamp. Lit also means "set on fire," like a lit campfire or a glowing, lit stick of incense. If you're studying American literature in school, you might describe it using the colloquial shorthand, "American lit."