A standard set of golf clubs usually has a pitching wedge (PW) and a sand wedge (SW).  The normal loft for a Pitching Wedge is 45° and a Sand Wedge 55°.  

Many golfers also have what is call Gap Wedge which 'fills the gap' by having a 50° loft and there is also a Lob wedge which has 60° of loft. Generally speaking the greater the loft the less distance the ball will travel and the reason for having more wedges is simply that It is often easier to take a full swing rather than try to control short distances with a half or three quarter swing.

Click on a video below to view:

When should I consider buying more wedges?