Tezos is a blockchain that has a unique feature which improves itself over time by using a formalized process of upgrading to its protocol. In theory, this workflow is similar to how shareholders in a corporation work where they get to vote on a future direction for the corporation.
Formal governance structure in this case does not exist in many other blockchains. As a result, new projects are often decided by a small group and imposed on the whole ecosystem. This process can potentially result in hard forks when participants don't agree with the decisions. Hard forks can split the chain into two or more chains that can co-exist and split the community. Thus, Self-amendment aims to avoid this scenario, by allowing token holders to vote on the future development of the blockchain.
The self-amendment process is composed of five periods:
Each of these five periods lasts five baking cycles (i.e. 20,480 blocks or roughly 14 days), taking almost two months from the proposal to activation. The latest and current self-amendments are available at tezosagora.org.
Should there be any failure in a given period, the whole process will revert to the Proposal Period, effectively aborting and restarting the process.