From a mechanical perspective, math is more simple: roll 1d20 plus modifiers vs. a Difficulty Class (or Armor Class) with higher rolls always being better. Characters all progress as the same speed (xp chart), and in theory are fairly balanced against each other (there's an ongoing martial vs. caster debate that I won't get into). There's lots of customization available, from backgrounds, subclasses, and feats, allowing two characters of the same class to feel completely different. Unfortunately ability score benefits became linear, so they're super-important (and generally bloated). Speaking of bloated, hitting is easier, but everything has way more HP, making combat less swingy (and more of a slog).
There's been a lot of changes to social conventions as well. Since I'm old, I don't want to get into that. Now you kids get off my lawn!
There's been a lot of changes to social conventions as well. Since I'm old, I don't want to get into that. Now you kids get off my lawn!