The abs light normally goes off after just a few minutes but now it stays on what is the cause?

It means you take it into the shop so they can find out why. Without knowing what codes the computer have...nobody can guess which of the many reasons it could be.

It means the computer has detected a problem with the ABS system and it needs to be checked and repaired.

In case you're wondering what it's about....ABS is Anti-lock Brake System...not really something you want to fool around with in most cases.