Plug and spike lawn aerators get oxygen into the soil and roots of a lawn, but plug aerators are better overall than spike aerators.
But although both have advantages, plug aerators are better if your soil is severely compacted, as they actually "Remove compacted soil" from your lawn, freeing up space for the lawn to grow.
Plug aerators also allow more water, oxygen, and nutrients to reach the roots of your lawn.
A spike aerator should do the trick if your yard has relatively loose soil or you want to keep it from getting compacted.