BTO is used to emphasize that what you just SAID was completely the opposite of what you actually MEANT. This allows you to covertly talk to friends during conversations in public and is an easy way to get your message across while texting.
Girlfriend: "I think it would be fun going for a walk and talking about our feelings today instead of watching football and drinking beer all day. Doesn't that sound fun?"
Boyfriend: "Yeah it sounds great...BTO!"
Megan: "Maybe instead of watching football and drinking beer this Sunday we should go for a long walk and talk about our feelings."
Eddie: "That sounds like a great idea...BTO!"
Example 2, when referencing fugly peeps: "That girl is banging hot...BTO!"