For the first time since 2011 I have a full node up and running. Two different machines. My question is what does a node save and what doesn't it save pre wallet era. When I was mining we didn't have wallets showing all the coins available.
The Bitcoin blockchain runs on what is known as a public ledger which contains a hierarchy and stack of transaction data and origin including time stamps in a particular arrangement through something known as Merkel tree. Basically running a node simply means having a copy of that public ledger. The fact is all miners run nodes the difference is being able to use hashrates to include transactions in a block and also confirm them.
One of the advantages of running a node is if you have a wall you can use your node to broadcast transactions meaning you have increased privacy since you are not depending on other nodes.