MTHFR is a gene involved in processing folate; common variants of it (C677T and A1298C are the ones test reports name) run through a large share of the general population. It gets asked about constantly in vein communities — usually as "do you have the MTHFR mutation?" — because it was historically linked to clotting via homocysteine levels.
The honest current picture: carrying a common MTHFR variant by itself is not considered a meaningful clot risk, and major guidelines no longer recommend routine MTHFR testing in clot work-ups. That distinguishes it from the thrombophilias that do carry weight (Factor V Leiden, prothrombin mutations, antiphospholipid syndrome — the things an actual clotting work-up looks for after an unexplained DVT).
Where that leaves you: an MTHFR result from a consumer gene test isn't a diagnosis or a treatment trigger — but a personal or family history of clots absolutely justifies asking for a proper thrombophilia work-up, whatever your MTHFR status. Bring the history, not just the gene report.