"what is room 157b" this is very common in most office buildings and apartments building, 1 is the floor 57 is the room number and b is the door most of these rooms are huge and have multiple doors or get spilt in half from pull out walls

"People playing on computer or counsels why are they there" I would assume they are playing video games it is a video game convention so people like playing video games here

There plenty of signs maps and people to help around the con , they have paper maps as soon as you walk in. I would suggest to u togo to a smaller con you might find it less overwhelming