What is a role of beta lactamase inhibitor?

Some bacteria produce beta lactamase enzyme, this enzyme will break the beta lactam ring structure of certain antibiotics (penicillin, cephalexin for example) rendering them ineffective against the infection. If you add a beta lactamase inhibitor to a beta lactam antibiotic (i.e clavulanaic acid added to amoxicillin) it decreases the potential of the bacteria to inactivate the antibiotic.