Lucid dreaming is controlling your dreams.
Astral projection is your soul leaving your body.
Both take place in the astral plane, however lucid dreams are a completely subjective creation & are subject to lower vibrational frequencies, meaning usually less lucidity, control, power etc. While astral projection operates in higher frequencies, and is a co-creation of many beings, and unlike dreams, they will not cease to exist when you’re absent.
LDs are safer & easier. AP is more difficult to achieve & there are consequences for your actions/thoughts/feelings.
One is real and the other is not.
One is a dream where you know you are dreaming (Lucid)
The other is a dream where you don’t know you are dreaming and you think you travel the astral plane