A champola is a horn passage of four to eight bars in the montuno, in which two or more different phrases run through each other. The horns join in layer by layer, making the montuno fuller and more complex.
According to Wikipedia, champolas, complex horn arrangements, are among the innovations that set timba apart from salsa.
All three are horn passages in the montuno, but they are built differently:
The dancers Osbanis & Anneta use the word more broadly: for the mix of all the instruments, not just the horns. Piano, bass, percussion and horns each play their own part, but together they sound like one whole.
In Cuba a champola is also a milkshake of guanábana, milk, sugar and ice: separate ingredients that together form one flavour.