How do the sects of Judaism differ?

It depends what part of the world you look at:

In North America there are four main branches of Judaism:

• Orthodox, who are traditional
• Conservative, who try to walk a middle ground between Orthodoxy and Reform
• Reform, which is liberal and places less emphasis on "rules" and more emphasis on personal responsibility.
• Reconstructionist, which is in some ways more traditional than Reform, and in other ways more liberal.

(North America also has "humanist" congregations which generally do not believe in God, and unaffiliated synagogues.)

In England there are 4 main types

• Orthodox
• Masorti
• Reform
• Liberal

In Ireland and most other countries there are 2 main types

• Orthodox
• Progressive

In Israel there is only one official type

Orthodox (However other denominations are now starting to get a foothold.)