There are 66 wards in Philadelphia. Wards are broken into divisions. Three of those wards (39, 40, and 66) have so many divisions in them that the Democratic Party divides them into two wards for representative purposes. It is customary to refer to your ward by number. For instance, I live in ward 55. This is mostly the Mayfair section of the City of Philadelphia.
You can see a map of the various wards here.
Wards are led by a ward leader. Each party has a ward leader that oversees party activities in that ward. This includes things like voter registration drives, party endorsements, and distribution of patronage positions.
Our ward leader on the Democratic side here in Mayfair is Bob Dellavella. He has been ward leader for several terms. A list of ward leaders (which may or may not be current) can be found here.