Maintenance is what happens every 2/3 weeks to nails to keep them in good shape. A maintenance appointment can vary depending on what the client has, ie a natural l&p nail will only require a rebalance with one colour, a French rebalance will require the white tip to be re-aligned as it grows out, to make it look like new again, as well as rebalancing the pink body of the nail.
The word rebalance should mean that several things are done with the nail, for beauty and balance, ie shortening, thinning of the free edge, re-placement of the apex (which has grown up the nail), and replacement of product in the new growth area.
The confusion arises because some techs just "infill" - which is really just filling in the gap with not much else done. In my opinion, every time you do a maintenance appointment, you should be rebalancing the whole nail to make it strong and beautiful.
Sometimes a French rebalance (re-aligning the white) is called a "backfill".
Gosh, no wonder the general public get confused!!
I hope this helps x
Edit: Backfill does not refer to the cuticle work
