What is an aspect in opinion mining?
It can be explained with a simple example:

EXAMPLE REVIEW: The dashboard finishing is not good, indicators, headlights, 
parking lamps and ac vents are having impressive finishing
The overall car is good.

The statement "overall car is good" indicates that there is a mix of positive and negative opinion about the car. In the aspect of the dashboard, the opinion is negative. However, the review apprising the aspects "indicators, headlights, 
parking lamps and ac vents".
It might be clear by this example that the aspects are the properties or factors of the target product or event.