What enables ice skaters to skate fast and why is ice slippery?

I think you are referring to the changes caused in the
physical state of ice during ice skating and why ice is
slippery.

There are two theories to explain why ice is
slippery and why an ice skater can skate at a very fast speed. One states that when a
person wearing ice stakes passes over ice, there is heat generated due to the kinetic
friction between the stakes and the ice. This melts the ice and creates a very thin
layer of liquid water. The layer of water acts as a lubricant and reduces the
coefficient of friction to a large extent. This makes it possible for ice skaters to go
at very high speeds. As soon as the skater has moved forward, the water layer solidifies
back to ice.

Another theory states that when ice is formed
water molecules on the top layer of the sheet of ice are not exactly frozen. Due to
their vibration, they remain in a quasi-liquid state. This layer of liquid, again, acts
as a lubricant reducing the friction between the ice skates and the ice to a large
extent.