Scarification and aeration are two different lawn care processes. The primary goal of scarification is to remove thatch and other organic matter from the lawn. Aeration means poking holes in the lawn to improve air flow and drainage.
However, scarification and aeration can sometimes both be done in the same action. Scarifiers tend to leave holes (or ‘scars’) in the ground, and as such, they have an aerating effect. However, if you want to aerate a lawn that doesn’t need to be scarified, the healthier solution would be to use a purpose-made aerator that will less severely impact the grass.