class how to..

Hey freinds,
Iam new in programmering world. I have a bit diffeicilit too understand how too work whit classes.
Yesterday i saw a code....its confusing:The code wass somting like that  see my code!:

i want to know:

1) why in the code the say  Icar thiscar=met.dns(); and not car=met.dns(); - Here why the do not do this
Car = new car(); and  then  car=met.dns(); 
 
 1 Interface Icar
2 {
3 name get{} set{}
4 age get{} set{}
5 carpatenumber get{} set{}
6 }
7
8 Car:Icar
9 {
10 }
11 -------------------------
12 Icar thiscar=met.d ...