Aspect (/ˈæspekt/) is a property of verbs which describes the temporal flow (or lack thereof) in the described event or state to which the verb applies. In other words it tells us something about time.
There are three aspects in English. The default is the simple, which is really lack of aspect. The two real aspects are the perfect and the progressive (aka continuous), either or both of which can be applied.
Generally speaking, the perfect aspect indicates something finishing, whilst the progressive aspect indicates an action that starts and continues for a time before stopping.