An infill is where you fill in where the product has grown up from cuticle area with your chosen product, a rebalance is when you replace your smile line to where it should be and i class both as maintainance
An infill is a quick service that just fill in the regrowth area ... I never do it.
I always rebalance which means I maintain the balance of the whole nail structure at each appointment ... takes a bit more time but saves clients from becoming disheartened with wearing nails which break much more frequently when only filled in. I like to keep my clients problem free .... which I always endeavor to do.
All regular appointments are classed as maintenance a that what you are doing .. maintaining that initial full set and keeping it looking beautiful.
When you replace the smile line of a Pink and white set of nails it is known as a Forever French or French Rebalance.