Red means 'Stop'; you must not go beyond the traffic light.

When red and amber show together, this also means 'Stop', but indicates that the lights are about to change to green.

Green means you may proceed, provided you can clear the intersection during the green phase and your entering the intersection does not pose any danger to other road users.

Amber means ‘Stop’. Only if you are already so close to the traffic light that stopping would mean having to brake hard may you go on when the amber light appears; amber also indicates that the signal is about to turn to red.

A green arrow under a red light: this means that you may turn off in the direction indicated by the arrow, provided that you first stop at the light before proceeding without hindering other road users who have a green light.