The A,B,C and D are aircraft weight categories. The 1600m and the 2000m are the minimum visibilities that must exist in order to legally execute the approach. You are correct that ALS is the Approach Lighting System. At some airports the visibility minimums increase if the ALS is out.
A B C D is approach speed category, so A is Vref up to 90kts, B 120kts, C140 and D 165 knots. If YouTube plane doesn’t give you a Vref it is 1,3xVs in landing configuration if i recall correctly.