MTHFR
MTHFR — the molecular target that 1 compounds in the wiki act on.
In one line: The enzyme that activates folate — some people have a slower version and do better with the pre-activated form.
MTHFR converts folate (vitamin B9) into its active form, which your body needs for "methylation" — background chemistry that runs DNA, mood, and detox. A common gene variant makes this enzyme slower, so those people may do better taking the already-active form (methylfolate) rather than plain folic acid.
It's why quality B-vitamin supplements use the "methylated" active forms — they skip the step a sluggish enzyme struggles with.