A failure is a term used to describe an issue with the computer or a device that prevents it from functioning properly. For example, when a hard drive fails (hardware failure), it prevents the computer from booting and prevents it from working again until it is replaced.
Although a failure is associated with hardware, any problems with software may also be referred to as a software failure. With most software failure, you'll usually encounter an error to indicate the type of problem. A general failure is a non-specific failure that could be caused by software or hardware.