An aspect of something is one of the parts of its character or nature.

The aspect of a building or window is the direction in which it faces.

If something begins to have a new aspect, it begins to have a new appearance or quality.

In grammar, aspect is the way that a verb group shows whether an activity is continuing, is repeated, or is completed. For example, in 'They were laughing', the verb is in the progressive aspect and shows that the action was continuing.