Answer:
Conversion
Step-by-step explanation:
The best thing to look out for when checking how a post is performing is the conversion.
Conversion is the number of people that your post was able to bring to partake in or buy your products.
This is very important because, it is the aspect that will show that the money you spent on the promotion of the post is not wasted.
It should be understood that others like impression, clicks, share etc are just to show you that people are seeing your post. This is because those ones are not actually going to bring any money to you.