Un_Dieu posted...in general
I mean the boring answer is they're just better at everything(on average).
A few that stand out to me are
Champion mastery
-Builds, summoners, power spikes(lvls and items), matchups, knowing cooldowns, etc.
-People know when they're stronger than their lane opponent and will punish you instantly if you overstep.
-Target prioritization in skirmishes/teamfights.
Map movements and using/creating pressure
-Pushing when you have lane advantage and disappearing to ward river/jg, threaten roams/invades, or steal camps.
-Roaming(mid roams top/bot, bot roams mid/top, top roams mid or tp's bot). When/where/how, who has what summoners up, etc.
-Knowing what to do after taking towers. Does bot rotate mid? If mid has easy waveclear maybe you go top? Is drag still up? Maybe stay bot/mid until drag is down. Is your mid laner a good split pusher like Leblanc, Yasuo, Ekko, Kassadin? He should usually swap bot after tower drops. Drag down and tower dropped, maybe bot should swap top against the no waveclear tank. Things like that.
-Late game stuff like lane assignments, knowing when you can sneak/rush drag/baron, trading objectives, pushing all lanes with baron buff, etc.
Tower dives(sort of branching off of above)
-If you play a weak early game champ or get chunked super hard and try to stick around you better believe you're getting dove. Regardless of when it is. 4 man dives bot, top/jg/mid diving top, mid/jg/support diving mid. It's going to happen, and if you dont respect it you're dead and lane is over.
-General diving things like trading aggro, tanking as many shots as you can before dropping, who initiates, comboing cc, etc.
Obviously there's a lot more but it's still early and i cant think of the rest rofl. Not everyone above that cutoff is perfect at all this stuff but generally the execution/knowledge will be there for a lot of players for most of it.