English words MUST be kept as is and translations added after them. Example: ["account", "accounts", "wallet", "wallets", "conto", "conti", "portafoglio", "portafogli"]
Nodes participate in the Monero network and secure @transactions by enforcing the rules of the network. Nodes download the entire @blockchain to know what transactions have taken place. Nodes assist the network by relaying transactions to other nodes on the network. Nodes may also choose to contribute to the Monero network by participating in crafting @blocks (this is called @mining).
<sub>1. *Fluffypony gives a great explanation of why mandatory network upgrades are good for Monero.* ([Monero Missives for the Week of 2016-06-20]({{ site.baseurl_root }}/2016/06/20/monero-missive-for-the-week-of-2016-06-20.html))</sub>
The Monero Core Team plans for a network upgrade roughly every 6 months. At that time, if you are running a node it must be updated to the most recent version of the Monero software or it will no longer be able to participate in the network.
The rules that nodes follow are built into the Monero software; When all nodes agree about the rules to follow this is called @consensus. Consensus is necessary for a cryptocurrency because it is how the blockchain is built; If nodes don't agree about which blocks are valid, for example people who have not updated their Monero software, those nodes that don't agree will no longer be able to participate in the Monero network.
