The purpose of a soft fork is usually to improve the efficiency or security of the blockchain network by implementing new features or rules.
Soft forks are typically implemented through the activation of a new rule that is backwards compatible with the existing rules.
Soft forks are often used to introduce new features such as Segregated Witness (SegWit), which increases the block size limit by removing signature data from transactions.
Soft forks can be contentious if there is disagreement among nodes about the proposed changes. In such cases, there may be a chain split if a portion of the nodes refuse to adopt the new rule
Soft forks can also be used to reverse transactions that are deemed invalid or fraudulent, as was the case with the DAO hack on the Ethereum network in 2016.