Can you tell me what is wrong with my plant? Will it spread to other plants?

Hello, Kaitlyn.

From the picture it looks like you have mealy bugs on your schefflera plant.  Use “Bonide” Insecticidal Soap to help control.  Thoroughly spray the insects, including the undersides of the plants leaves.  Repeat treatment weekly or bi-weekly if needed.

Check her other plants to see if the mealy bugs have spread and treat them as well.