it does not give you eitr meter. The same way that health potions don't add to your health total, but the text implies that it might.

it restores eitr like others restore stamina and hp. but you need atleast 1 eitr based food of the 3 available currently to even have eitr bar to begin with. without such a food the potion is useless.

Okey thanks:) Guess I just did not notice the difference xD

It briefly boosts your eitr regeneration. This is easiest to observe while using the frost staff.