I am searching for an appartement in Germany and I came across "1. Etage" which is normally the first floor.
However some countries have first floor for ground floor so I am confused now and I don't want to stay on ground floor.
As said in knut's comment there are regions in Germany - especially in southern Germany - where people understand the term "1. Etage" differently than in the rest of Germany.
... especially people who do not deal with buildings professionally (such as architects or estate agents).
So if the description has been written by a private person and the house is located in southern Germany you have to ask the building's owner if "1. Etage" means "ground floor" or "first floor above ground floor". Use the wording "Erdgeschoss" and "Obergeschoss" to make sure you are talking about the same.
If the description has been written by a professional or the house is located in northern Germany the other answers are right.
After reading the comments:
It is not "southern Germany" in general, but only in some regions of southern Germany where "1. Etage" means "ground floor".
However in parts of eastern Germany this is also the case.
One comment says that the button for the ground floor in the elevator in a building in Dresden is named "1" which is not the case in any part of southern Germany.
Due to this fact it may be possible that in eastern Germany (or some regions there) even official documents (from architects or state agents) name the ground floor "1. Etage".
There's even a difference(1) between American and British English and some regions in Germany use the terms as in US, others use the GB terms.
This is in wide parts of East Germany:
It even may depend on the owner of the building how they name the buttons on the elevator, so it may be mixed up even in the same regions.
I too noticed that '1. Etage/Stock' is sometimes used for ground floor as well as the floor above, depending on who you're asking.
The official line is that '1. Etage/Stock' refers to the floor above ground floor GF.
Source: I moved into a flat in Berlin recently. When I was asked at the Citizens Registration Office about the floor my flat is located, I told the official that I'm not sure about the nomenclature and he explained it to me. Now my registration form says '1. Stock' and I live one level above GF.
If somebody is naming a floor "1. Etage" you can assume that it is the first floor above ground.
As you can see from the other answers it is not that easy if you take every edge case into account but these are rare cases and the writer will know that he can only use this term within a certain group of people.
Some buildings have different signs and elevator buttons but in every case I know this has spezial reasons mostly because of different ground levels around the building:
The building is at a rather steep hillside (The "Erdgeschoss" is on one side on ground level and on the other side above ground)
The main entrance is above ground level (Hillside again or flood protection or just a fancy architecture)
Some Buildings are constructed with half stories. So you enter on "Erdgeschoss" than you take the stairs to the "1. Etage" but it is only half way up on the other side of the building. The next stairs will take you to the "2. Etage" which is right above the "Erdgeschoss" the next stairs ends on the "3. Etage" which is right above the "1. Etage" and so on.
Sometimes existing buildings next to each other are connected and the owner wants to have similar floor names in both.
And a very special case can happen if a plan is made but is it not decided yet which floor is above ground level. But hopefully this is not the case for the apartment you are looking for ;-)