Wut do they mean by ';fill'; ur acrylic nails?

I'm getting mine filled tomorrow, wut are they going to do?Wut do they mean by ';fill'; ur acrylic nails?
When 2 weeks pass, you natural nails grow some and you can start to see where your nails are and where the acrylics are. Most women don't like this and get a fill. The nail tech will check you acrylics for ';lifting'; (starting to not stick to your natural nail), prep your new nail that just grew out, and reapply Acrylics to those areas. Also, if you have a set of pink%26amp;whites (an acrylic French Manicure) every fourth week you will need to get a backfill for the white portion.Wut do they mean by ';fill'; ur acrylic nails?
repair
after you have acryllic nails for a while, they start to grow off your real nails, so at the roots by your cuticles, show ur real nail (if that makes any sense) so the fill that area back up so it is acryllic again. kinda hard to explain but i hope you get it!