What is known as a ‘blockchain’ is a network of nodes which have identical copy of a file. The blockchain nodes are looking to reach consensus and then periodically add a block.
Not all blockchains offer smart contract capabilities. From the one that offer it - there are various programming languages used.
A person can run a node of a blockchain.
A person can also create and/or use a decentralized app / Dapp to call smart contract functions of a blockchain and do transfers.
Blockchains do not have servers - again, blockchains are a network of nodes.