LUT

A LUT is a table of colour translations, usually shipped as a .cube file, taking every input value and mapping it to an output. Two kinds get used for different reasons. A technical one converts flat log footage from a particular camera into a normal viewing space, and it is tied to that camera and profile. A creative one applies somebody's taste in a file.

The mistake is treating either as a grade. A LUT assumes footage arrives correctly exposed and balanced in the colour space it was built for. Hand it something darker or warmer than that and it exaggerates the error, so correct the shot first and apply the LUT after.