Bitcoin nodes are basically storage devices, such as laptops or PCS with Internet access, which have the capacity to store blockchain bitcoin. The nodes relay information from the user to the miner. They also hold blockchain bitcoin.
These nodes are synchronized with each other. If one node is offline ata certain time, it will download new data from the other when it is reconnected to the Internet.
Just like the Google sheet you access with moda view-only. If you have access, you can open that sheet online at any time.
If we end this analogy here, it's known as client client. However, client client cannot be named as nodes. To be a node, you have to be a full client. Full client is a client who has a blockchain and also shares block and network transactions.
Whoever has a vault with enough space and is connected to the Internet can run nodes.
Nods don't have to mine for bitcoin. All the miners are nodes, but not all nodes are miners. However, nodes are an important part of the ecosystem because they play a role in decentralized pathways, as well as blockchain security. Thank you, nodes!