Ground Effect

This topic usually is considered difficult to understand and many of my friends have been confused by it. Let me  try to explain it here in my own words, not in depth but conceptually. I would recommend reading multiple books or sources to get an accurate picture. Hopefully its easy to understand.

Ground effect occurs within a length of one wingspan over runway....in this ground effect, the induced drag reduces and giving a false sense of lift....hence during takeoff aircraft may take off at say 50kts instead of 60kts...but if we come out of ground effect immediately..there is not enough lift and aircraft will sink back...hence if the aircraft   lifts off earlier in ground effect...its recommended that maintain in ground effect till the a/s increases to required i.e. 60kts and then come out of gnd effect.
gnd effect occurs since the downwash (wingtip vortices) are effected by the runway or ground.