I’ve seen an incredible number of people who were never taught to properly touchtype and where each finger goes and developed bizarre techniques to type with 4, 6, or 8 fingers that may be almost as fast as the proper one but horrendously non-ergonomic. Ubiquity of staggered layouts (instead of proper ortholinear) does not help — it’s almost like it’s begging to type Z with ring finger and X with middle one.
AC means Alternating Current, electrical current that periodically reverses direction, and DC means Direct Current, a current that continuously flows in one direction. AC/DC on a socket means it can take both types of power.