Include, one cannot live without the other. The use case 
must include another use case. For example when you create 
an order you always must verify name etc. 

Extend, one can live without the other only some instances 
the use case will extend to another use case to do some 
stuff. For example, you can create an order but if the 
order is for a new customer you possible have to do 
additional check which you do not have to do for existing 
customers. In that case you can have an extend use case.

For Component:- A Component may use interface called import
                A Component may realiase from interface 
called export