Nowadays, the concept of space weather comprises the more active and dynamic phenomena of the general solar-terrestrial relations them. The lecture deals with the question of how the cyclic solar activity affects the earth and the near-earth environment. The focus is on explosive events such as coronal mass ejection and solar flares. Increased flows of charged particles and energetic electromagnetic radiation have a direct impact on manned space travel and satellites but also on technological systems on Earth. In addition to these rather short-term phenomena, the lecture covers also topics on much longer time-scales such as the impact of solar activity on the Earth's climate. Subjects covered in the lecture are: physics of the active Sun, the atmosphere and the magnetosphere of the Earth, the impact of space weather on technical systems, prediction of space weather, solar activity in the context