This is the 10945th most frequent Swedish word.
lysas
"Lyser" in Swedish means "to shine" or "to emit light."
Here, 'lysas' is used in the idiomatic sense of something being lit or shining.
Lampan börjar lysas när du trycker på knappen.
The lamp starts to shine when you press the button.
In this sentence, 'lysas' indicates the passive voice action of being lit by an external source.
Himlen lysas av månskenet.
The sky is illuminated by the moonlight.
The word 'lysas' here interacts with 'upp', forming a phrase meaning to be lit up or brightened.