We require friction for walking or running or driving, that is, the surface that we think of as non-slippery are the ones that provide some friction to our motion. Liquids, when spread over a surface, reduces the friction that surface can offer to another surface. This happens due to low shear of water and many other liquids. Because of this the two surfaces do not come in contact with each other at as many points as two surfaces without any liquid would. This reduces the friction and we perceive the receiving surface as slippery.
Loss of friction can be very dangerous, think about film of oil on a road surface or wet bathroom floor. That is why we wear rubber slippers and use rubber tyres for vehicles.
Hope this helps.
Wet surface has water in between the surface and legs of a person. Water decreases forces of interaction between surface and legs, hence LESS FRICTION is caused. This less friction , ( thus, act like a lubricant) causes more movement, hence a person slips.
the lesser the friction the slippery it gets
The wet surfaces are more slippery because, when some water or a liquid is spread on the floor, the roughness of the floor is decreased at that instance.
For us to walk on a floor the friction between our foot and the floor acts an important role for us to walk. So when we try to walk on that floor which is wet, as the roughness is gone (lack of friction) and when we try to walk then we tend to fall or it will be slippery.