Solar Wind is an important part of space weather. It is a stream of electrically charged particles, mostly electrons and protons, that are ejected from the surface of the Sun (the corona).
Solar wind is not "wind" in the same way as we think of it on Earth but it does have some similarities. For example, it imparts a (very small) force and it can move things (slowly). Spacecraft with solar sails use the solar wind for propulsion.
It's important to monitor solar wind because it affects life and technology on Earth.