What are “solar winds” (or other such phenomena) and how do they affect spacecraft if space is essentially emptiness and vacuum?

Question

I’ve heard how space probes use their “sails” to make use of “solar winds” to travel distances. But isn’t space just vast emptiness with no resistance/ friction?

In: 4

Answer 1

Emptiness with block of matter and sometimes speeding waves of particles that will push you more gently than an asteroid.