What is a mortal sin, and what are 15 commonly committed ones?

15 MORTAL SINS CATHOLICS ARE MISSING IN THEIR CONFESSIONS
Catholic Guides, 2 March 2023
https://www.youtube.com/watch?v=wskXw5MUgyA

I distance myself from the reference to 1983 code. But the list is correct.

Obviously fasting is not obligatory for a man suffering from a bodily ailment. But even so, abstaining from meat on Fridays is usually feasible./HGL