Circumcision prevents balanoposthitis. Without a foreskin, there can of course be no posthitis and hence no balanoposthitis.
An uncircumcised boy should be taught to clean his penis with care to prevent infection and inflammation of the glans. Cleaning of the penis is done by gently, not forcibly, retracting the foreskin. The foreskin should be retracted only to the point where resistance is met. Full retraction of the foreskin is usually possible by age 5, but some boys are not able to retract their foreskins until the teen years.
The term "balano-", referring to the glans of the penis (or clitoris), comes from the Greek word "balanos" meaning acorn. The term "-itis" means inflammation. So, balanitis = inflammation of the glans.