Preset vs profile
A preset applies a set of slider settings to your photo in one click: exposure, contrast, colour and more, which you can still fine-tune afterwards. A profile sits a layer deeper and decides how your RAW file is translated into an image to begin with. In short: the profile is the starting point, the preset is the look you lay over it.
Because a profile handles the base interpretation of your RAW, it doesn't move the sliders themselves, so you keep all the room to adjust. A preset does move those sliders, which is exactly why it's so handy as a starting point for a consistent series. The presets on this site work on top of your profile: pick a look, then match exposure and white balance to your own photo. Tip: set your profile first (Adobe Color or Camera Standard, for example), then apply a preset.
Related terms
Prefer a look in one click?
The presets on this site set these adjustments up for you as a starting point, which you then fine-tune to taste.