Proposals to change or alter the Bitcoin network’s block reward, block size, mining difficulty and other major elements require a consensus from Bitcoin miners located all around the world. Typically, miners and the members of the Bitcoin community run Bitcoin full nodes, which operate as a decentralized architecture to spread out information across the network. Using this unique infrastructure, the Bitcoin community can decide on which implementation or change must occur to optimize the network.
The Bitcoin network allows two types of changes called soft and hard forks. A soft fork refers to a set of extra rules that are implemented onto the existing Bitcoin protocol. An example of a soft fork would be the introduction of Segregated Witness, a proposal to optimize the space in the current Bitcoin Core blocks, by storing some of the internal data outside the original transaction.
http://bravenewcoin.com/news/leading-mining-firms-move-from-bitcoin-classic-to-core/
