Let's answer the most common questions:

How does accidental forks happen❓

Different miners find a block at the same block height at the same time.

How does a blockchain correct for accidental forks❓

Over time, all the nodes will pick the longest chain and discard the shorter fork.

How is a hard fork update defined❓

An update that makes previously invalid blocks valid

How is a soft fork update defined❓

An update that makes previously valid blocks invalid

If an update reduce the block size limit from 1mB to 500kB, what type of update would that be❓

Soft fork update

If an update increase the block size limit from 1mB to 2mB, what type of update would that be❓

Hard fork update.

As Satoshi Nakamoto said:

Decentralized = better.