Multiple properties of the solar wind that affect the earth are summarized in this overview. 13 specific solar-wind parameters that influence geomagnetic activity, the plasma sheet, the ionosphere, and the electron radiation belt are catalogued: these include the wind speed, number density, magnetic-field strength, field orientation, Mach number, Alfven speed, electron-strahl intensity, and magnetic-field fluctuation amplitude. The solar wind at Earth is categorized into four types of plasma emanating from different morphological features on the solar surface and the systematic differences between the four plasma types is assessed. The solar-cycle behavior of the solar wind is examined in terms of the changing occurrence rates of the four plasma types emanating from the changing Sun. A 27-day periodicity in the properties of the solar wind and in the reaction of the Earth are investigated: the periodicity is owed to features on the rotating Sun. The strong intercorrelations between solar-wind variables are considered and the origins of the intercorrelations are explained. Large-scale structures in the solar wind are reviewed and the different types of geomagnetic storms that they drive are summarized. The mesoscale magnetic structure of the solar wind is examined, the impact on Earth of its current sheets and cellular structure is explored, and a non-randomness in variations of the magnetic-field direction changes at Earth is demonstrated. Sudden strong velocity shears in the solar wind are discussed and their impact on the magnetosphere is shown via a global MHD simulation. The magnetic structure moving outward from the Sun faster than the plasma outflow is discussed, and it is pointed out that the velocity of the magnetic structure should be used when calculating the motional electric field of the Sun. Finally, drawbacks to monitoring the solar wind from L1 are identified.