Memory loss, also often called amnesia, is an abnormal degree of forgetfulness and/or inability to recall past events. Depending on the cause, memory loss may have either a sudden or gradual onset, & memory loss may be permanent or temporary. Memory loss may be limited to the inability to recall recent events, events from the distant past, or a mix of both. Although the normal aging method can lead to difficulty in learning & retaining new material, normal aging itself is not a cause of significant memory loss unless there is accompanying disease that is responsible for the memory loss.
Transient global amnesia is a rare, temporary, complete loss of all memory. Anterograde amnesia refers to the inability to keep in mind recent events in the aftermath of a trauma, but recollection of events in the distant past in unaltered. Retrograde amnesia is the inability to keep in mind events earlier a trauma, but recall of events afterwards is feasible.
Memory loss has multiple causes including a lot of chronic medical & psychological conditions, trauma, medications, drug or alcohol abuse, & infections.