It is said that 'catches win matches', which makes the job of a slip fielder a hugely important one.
Many of the catches will be taken by the slips and so reactions have to be sharp.
Positioned on the off-side behind the wicket, first slip is alongside the wicketkeeper, with second slip, third slip etc following in the same direction.
First slip is normally about a foot or so behind the wicketkeeper.
This is because the ball flies faster off the edge when the ball goes finer.