Here are a few messages that might be conveyed through honking:
“Hello, I’m here!” Simply a way of announcing yourself, for example driving into an intersection or a traffic circle. Of course because everyone does that it turns into a honking cacophony and in the end I’m not sure anyone realizes who is coming from where.
“I drive therefore I honk” seems to be the prevalent motto in some places. No intersection, no turns, no traffic circles. Just a straight road and a lot of honking to keep you company.
“Get the bleep out of my way” – addressing other drivers. This sounds pretty much like a continuous honk.
“Get out of my way” – addressing pedestrians. More punctuated honking, repeated if the ‘offender’ doesn’t react immediately. Of course, this can also escalate – like this one time in Lima, when a colectivo swerved onto the sidewalk and honked its way to the next traffic light to avoid rush hour traffic. The sidewalk can double as an extra lane.
“Careful, vehicle around the bend”. Honking in the mountains, basically. Buses and trucks driving in the mountains honk at every bend and turn. Picture a bus driving uphill and a truck (also driving uphill) on the only other lane passing said bus just before a bend. There is no way to see who or what is lurking behind that bend or coming downhill. Just keep honking and hope for the best.
“Thank you!” A brief, friendly honk.
“Bleep you!” Honking in a specific morse-code like sequence can be the equivalent of giving someone the middle finger. After a concert in California, cars were lining up to exit the parking structure and people let loose. All in good fun, I should add.