The term "second floor" refers to a level or story in a building that is located above ground level and below any upper floors. In other words, it is one of multiple levels within a multi-story structure, with each successive floor being higher than the previous one. The numbering of floors typically starts from the ground level (or first floor) and goes upwards to the topmost level or roof deck. So, if someone says "I live on the second floor," it means they reside in a residence that has two levels above ground level - the main living area is likely located on this level along with other rooms such as bedrooms, bathroom etc.