It simply means you are the first person on your relay team to run :D
typically a relay has four "legs" or four different runners. Each must finish a specific distance (often one lap around course) before next runner can start. The first runner is the "first leg" of the relay.
anchor
200m Freestyle 100m Butterfly 200m Butterfly 200m Individual Medley 400m Individual Medley 4 x 100m Freestyle Reley (First Leg) 4 x 200m Freestyle Relay (First Leg) 4 x 100m Medley Relay (Butterfly Leg/Third Leg)
Swing your arm right round from your sholder, start with youre arm bent, then thrust as hard as you can, release the ball when youre arm has gone past youre leg and continue to swing youre arm round
Each segment of the relay is referred to as a leg.
last man
IT means 'she of uneven leg length'
8.8 secs
Leg
It depends on what race you are running. For example In the 4x100 the 3rd leg is your closer he/she is the person who makes up for the lost time if the 2nd leg isn't fast enough and your 4th/ last leg take it home he's/she's your fastest.
at competitive galas, usually 4. occasionally 8. :)
steven redgrave