the most basic question, the difference between business and business casual

The title says it all. Can you please list the criteria for a dress code to be considered business/business casual? Although I understand that suits and ties means business and odd pants with odd jackets means business casual, and according to the rules we should wear balmorals with suits and bluchers for the latter occasion, i wanted to know what about this dress code that requires you to wear DRESS SHIRT AND TIE, BUT NO JACKET? does it fall under business or business casual category? Thanks in advance, and sorry for the caps lock, just to highlight the important stuffs.

Young and New to the Business World

I recently became a real estate salesperson. I am 19 years old. I want to dress to impress but I’m not sure how I should dress for the job. I want to show confidence and I don’t want to dress like all the older gentlemen in the office, since most of them are over the age of 50. Any advice on what I should wear or how casual or formal should I dress?

What Do I Wear at a Big Conference?

I’m going to a very big trade conference that’s being held in a major convention center. There’ll be a couple thousand people there at least. Do I need to wear a suit and tie, or just kakis and a dress shirt? (I’m not trying to get hired for a new job or anything like that.)