In British English, 'the ground floor' is the floor level with the ground, where we would often find a reception area. And the first floor is the next one up. In American English, the 'first floor' is the floor level with the ground.

I think this is a good explanation of how the terms are used in the U.S.: Normally there is a slight difference between the ground floor and the first floor depending on a commercial or residential building. Commercial structures refers to the entrance level as the first floor of the building and residential structures refers to the entrance level as the ground floor of the building and the first floor being above the entrance level. https://english.stackexchange.com/questions/69841/ground-floor-vs-first-floor

Are the ground floor and first floor same?Or there is a difference? It's a mess. Region-dependent and even then, no it's still a mess. . Expect anything, anywhere. Differences form building to building. "Ground floor" usually means that floor that you can walk in off the street or ground. This is meaningless for buildings on hills with entrances at different levels. Two obvious sequences of floors ...B2...B1... G ... 1 ....2 ...3 ... ...B2...B1... 1 ....2 ...3 ... One has a "ground floor" the other, not so much.

In British English, the first floor is one floor above the ground floor. https://speakspeak.com/about-english/ground-floors-and-first-floors-in-british-and-american-english

They are the same in English.