Pardon me...what's the difference between Go go bars and discos and host clubs?

Go Go Bars - there will be poles on the bar tops and the men/women will be dancing on it. If you like any of the "dancers", you can bar-fine him/her for short time or long time. Usually the dancers are from poorer outer province from North or Issarn (North East).
Disco - actually I don't think Thailand has "discos"... more like pubs and restaurants. When we think about "disco", there's usually a big dance floor where people will be dancing in it but in Thailand, the dance floor is a small one and its usually only in the house music "zone". Thai prefer to stand at the tall table with their whiskey on hand and listening to live music, occasionally singing along. You can find nice clubs at RCA or the more "hi-so" crowd at Ekkamai/ Thonglor.
Host Clubs - usually call the "member's club" where it is cheaper if you sign up as a member. They usually have a big lounge with nice big sofas. Like the KTV in Singapore, the mama or papa-san will bring the men and women to you and let you choose who to sit with. They usually charge by the hour. More expensive than gogo bars. Nice place to hang out, to listen to live music and to entertain your business friends.