The style might be described as (exaggerated) Realism -although his style is realistic style - which means that the subject/scene is painted as true to life as possible -Botero exaggerates everything in the scene: the people, their poses; the details.
To help in future: here is a list of various styles of painting. Next time you have a question like this you can click on the description of any style and compare it to the style of the picture you are looking at.
