When we are moving in any direction at any speed this will change our experience of the wind. Both the wind angle and the the wind speed will change so that we no longer experience true wind but are now experiencing apparent wind.
As an example imagine that the wind is blowing from the North at 10kts but we are sailing North East with a SOG of 5kts. Our motion combined with the existing wind would create an apparent wind speed in excess of 10kts and move the apparent wind angle around towards the east slightly.
As a result of apparent wind it is possible for some boats with very low drag (such as multihulls and planing monohulls) to sail to windward at speeds in excess of the true wind speed.