Adds texture to the surface.
No washing of brushes.
Uses a lot of paint.
Not terribly accurate.
The beige and burnt sienna painted with palette knife.
If you make a mark with the blade you will get a sharp straight edge, often thicker at one end than the other.
There are many sizes and shapes of palette knives. It pays to buy from a good art supplier. I bought several very cheaply and all were rigid and unresponsive. The one in the photo is from Daler Rowney. It's springy and feels good.
I'm not a fan of paintings wholly completed by palette knife, I think they leave too much to chance, but every so often a well aimed smear is just the job.