Common B1 in the elevator

What are the abbreviations for B1 and LG commonly found in elevators?

There are more high-rise buildings, and the elevators are naturally not too small. I wonder if you have seen such signs as B1, B2 or LG when you take the elevator?

As we all know, F refers to the floor, which means "floor". What does B or LG mean?

B is actually the abbreviation of basement, basement means "basement, the bottom of the building", so commonly used B plus numbers to indicate several layers underground.

LG is also common in some large buildings. It is an abbreviation for lower ground, which means "underground." Many buildings often use LG and L when marking the location of the business. If they are missing, it is likely to confuse the ground and the ground.

Also note that although LG is an abbreviation for lower ground, the individual L is not an abbreviation for lower, which corresponds to the word level, which means "layer".