A mote is a small speck or spot. You might see a mote floating in the air when sunlight comes through a dusty window.
The word "mote" can refer to different things depending on how it's used. If you talk about a mote as a tiny bit of dust, it usually means something very small that gets in your eyes or is visible in a ray of light. But if someone says they're concerned with motes and beams (from the Bible), they might be talking about judging others for their own flaws - it's like saying, "Hey, look at all those tiny bits of dust on my shirt, but are you perfect too?" In this sense, the word isn't just about a small speck, but also about keeping an eye on our own behavior.
A small particle; a speck.
