what does antilock light on dash mean?

You should have this looked at. This means your anti lock system is not working properly. Your brakes will still work fine by the anti lock system is not backing it up. Could be a wheel sensor.

Yes, most often it is a wheel sensor, but it could be something more.

Yes, this is generally a wheel speed sensor.  You should definitely get this checked out.  If you have traction control, it generally will not work without the ABS fully functional.