How Data Travels

Imagine you want to send a giant LEGO castle to a friend, but the mailbox is too small. What would you do? You would take the castle apart and put the pieces into many small envelopes! On the internet, information like photos or videos is too big to send all at once. Instead, the computer breaks the data into tiny pieces called packets. Each packet is like a small digital envelope. It contains a little bit of the data, the address of where it is going, and a 'return address' of where it came from. Because these packets are so small, they can zip through wires and satellites at incredible speeds.

Once your packets are sent, they don't all have to stay together. In fact, they often take different paths! This is where routers come in. A router is like a digital traffic cop or a smart GPS. When a packet arrives at a router, the router looks at the destination address and decides the fastest way to send it to the next stop. If one path is 'clogged' with too much traffic, the router will send the packet a different way. This means Packet $1$ might travel through London, while Packet $2$ might travel through New York, even though they are both going to the same computer!

When the packets finally arrive at the destination computer, they might be out of order. Packet $3$ might arrive before Packet $1$! To fix this, the receiving computer looks at the sequence numbers on the packets. It's like having page numbers in a book. The computer waits for all the pieces to arrive and then uses those numbers to put them back in the correct order. This process is called reassembly. Once every piece is in its place, the computer shows you the finished photo or message. If a piece goes missing, the computer sends a quick note back asking for that specific packet to be sent again.