Once you add this extension to your browser and create a free account, you invoke the shortcuts using the forward slash ( / ) and instantly get a list of quick commands you can select.
So for instance, instead of writing down: "THE TECH-LETTER" as a heading, then having to go to font size and increase it to make it stand out...
... quick select one of gSweets' shortcuts to get that done faster.
At this point you might be thinking "Prithvi, it's changing a font size. It takes 2 seconds". You're absolutely right, if you're writing an essay that involves 1 header, this probably isn't too much of a gamechanger for you. But for those who write documentations or papers with multiple sections, you might want to reconsider.
Also, of course, there's more than just headings.