How does that water get on the inside of windows and what can I do about it?

How does that water get on the inside of windows and what can I do about it? Condensation on the inside of a window is the result of a higher air moisture content contacting lower temperatures on the glass. The higher the interior humidity & the lower the outside temperature, the more condensation can occur. Excessive interior humidity can lead to structural damage. Wood rot, mold & mildew can result.
Helpful hints:
~Check sashes for smooth adequate operation.
~Use exhaust fans, especially when showering.
~Install & use a dehumidifier.
~Use ceiling fans to circulate air.
~Open windows & doors whenever possible to allow interior moisture to escape.