1.
light, lamp, small flame
A small, warm light, especially from a candle, oil lamp, or similar source. Often evokes a sense of warmth, hope, or nostalgia.
2.
light (figurative), beacon, glimmer
Used figuratively to refer to something that provides hope, guidance, or spiritual illumination.
Register
A literary and poetic word. In everyday speech, 明かり or 光 is more common for "light." 灯 evokes warmth, intimacy, and a gentle quality of light, and is frequently used in literary and figurative contexts.
Writing
The kanji 灯 can also be read as ひ (as in 灯をつける). The reading ともしび specifically refers to a gentle, flickering light source and carries a more literary tone.