How Bitcoin Mining Work? [Technical]
In simple words, BFT lets a decentralized system function normally in an adverse situation when there is a malicious user in the system, or a fraction of the system fails.
When the majority of users in a system are ethical personals (i.e., people who follow the rules), they can override the malicious work done by non-ethical individuals. So for a system to function normally, at least 51% of users should adhere to the rules set up in the system. This gives rise to consensus, which is the general acceptance of specific rules and regulations.