“Can someone dim the lights?”
You're about to play a video clip in a presentation. The room is too bright, so you want someone who's standing near the switch to turn the lights down or off.
Can someone dim the lights?
Make a request this way when you don't care who does it:
Can someone help me with this?
Can someone come down and take a look at my computer? It's acting up.
The word "dim" means "not bright". So the verb "dim ___" means to reduce the amount of light.
You can "dim the lights" in a room, which means to make the room less bright. Sometimes lights have a switch that allows you to dim them without turning them off. If the lights only have an "on/off" switch, then "dimming" the lights means tuning them off.
You can also dim things like a computer screen or TV.