A rebalance is what a lot of people call an infill, but a rebalance involves addressing all area of the nail not just zone 3. So, addressing hte length of the enchancement as well as the balance of the nail and whether the smile line needs moving. It's what is needed to keep enhancements looking good and being structurally sound.
L+P stands for Liquid and Powder - again most people call it acrylic, but that is incorrect because all nail enhancement systems (L+P, gel and fibreglass/silk) are chemically acrylic based.
hth's