What is an IIS application pool?

Question

What exactly is an application pool? What is its purpose?

Answer 1

An application pool is like a pond, if I create 2 application pools, first application pool has 100 fishes and another application pool has 200 fishes, here fish is like an application in application pool. They are managed by worker processes. Best advantage is: if pound number-1 has bad water and cases all fish are effected then there is security of fish in pound number-2. Like this if any application pool is effected by any problem but there is not any effect of this problem in application pool 2 so security in improve, and another profit is that is you provide all necessary authentication and rights to all applications in a single application pool.