You know about Capsule that are used in medical . And this contain many compound in it. Similar in Networking data is first Encapsulated and then send to its Destination. Encapsulation is important because to send data in its proper destination. as IN OSI Reference Model as data travel from one layer to other layer .Every layer add a header.
This header contain source and destination address .
basically header are added on the Transport layer ,network layer , data link layer and Physical layer.
