For example, are you hoping to get through a business lunch without embarrassing yourself, or are you thinking about how fascinating the conversation might be?
Some companies don't have a set lunch hour for the more important bosses, they may go on a long lunch, especially if it is a meeting - a business lunch we would call it.
" I'm going to an alumni lunch." " I'm going to a business lunch." In that case, someone may refer to a " lunch" without the word " business" or " alumni" or whatever particular kind of the event it is.