(Legal) liability is said to exist when a wrongful act or default can be attributed to a person (or company). In that case, that person is liable to compensate the damage that has occurred.
In terms of breach of contract, liability refers to compensating for damages in the event of non-performance of a contract.
A person may be liable for an unlawful act that they have committed (fault-based liability). In that case, we also speak of “fault”. However, sometimes one person is liable for the actions of another. This is called “qualitative” liability or strict liability. For example, a parent is liable for damage caused by their child (under the age of 14). Other forms of liability are production liability or professional liability. Many liability claims can usually be insured against.