Just a flavor question (with perhaps slight gameplay influence):
How does a wood elf use the Mask of the Wild trait to hide?
The wood elf's Mask of the Wild trait says:
You can attempt to hide even when you are only lightly obscured by foliage, heavy rain, falling snow, mist, and other natural phenomena.
Using fog as an example: Does the elf simply hide better in (lightly obscuring) fog, or does he more seem to melt into the fog through the magic of his fey ancestry?
Best Answer
The details of how it looks in-game are not specified, so it's up to you.
The description of the Mask of the Wild trait that you've quoted in your question is all that the books state about how it works. The description only explains the mechanics - you can hide when lightly obscured by natural phenomena - so what that actually looks like to other creatures is up to you.
Given that it doesn't automatically cause you to be hidden (it just lets you try to hide even when not totally obscured), a logical interpretation might be that your wood elf character is better at camouflaging themselves and blending into the natural environment around them.
The Mask of the Wild racial trait is briefly addressed in the Sage Advice Compendium:
As you can see, they're not automatically hidden, just able to hide where others wouldn't be able to be.