A Bitcoin node is a part of the network that allows Bitcoin to operate

A Node is a core part of the network that allows Bitcoin to operate. It increases security and improves reliability!

Any individual can run a full node by using the core client.

How to Break it down?

A Bitcoin Node is simply the Bitcoin Wallet client software. It allows an incoming connections from other Bitcoin client software.
It becomes a device where other wallets connect to your wallet  and shares information such as transactions, balances, etc.
It requires no maintenance as long as you have enough hardrive space to keep filling it up with every single transaction that happens and also every single block that gets mined.

Does it have any monetary reward? None.


1- It needs to run the node on your PC 24/7

2- The longer it keeps a stable connection to the internet and does not disconnect the more clients connect to your node. It uses a good amount of your internet data. The data usage is an average of 646 GB a month


Source: http://statoshi.info/dashboard/db/bandwidth-usage
Why Run A Node?

The more nodes the more secure the network becomes.


Nothing special… The more node  are connected to your wallet the faster your own transactions gets propagated across the network to other nodes. By doing so, you have a bigger chance to get into the next block. But once again, it is really not a reason to run a node.