To Scarify – is often a mechanical process nowadays which aims to lift material (typically moss) referred to as thatch (redundant and unwanted material) away from the root of the grass in order to give it some breathing / growing space.
In a lot of cases it is (or should be) only part of a wider set of garden lawn treatments and applications made to meet the goal of having a perfect lawn (or a quality lawn for the majority of people).
Scarification works as one tool in a range of others. It’s a great way to clear thatch, but it’s also destructive and will thin out the grass too. Mechanical Scarification is a robust treatment and does not discriminate!
Scarifying your lawn