ADHD

There can be some comorbidity / overlap, but they're different things.

ASD - typical presentation includes difficulty interpreting facial expressions / vocal tone / figurative speech, difficulty with theory of mind or modelling the experience of others, difficulty with social protocols or cues, inflexible, literal interpretation of rules, sensory issues, overload issues, single-subject fixation, spatial perception issues.

ADHD - typical presentation includes difficulty ignoring distractions, dificulty remaining focused on non-stimulating tasks, poor executive function, poor time management, poor task management, poor emotional regulation, forgetfulness, impulsivity, rejection-sensitive dysphoria, sensory/overload issues, fidgeting.

It's possible (and quite common) to have both; it's also quite possible to have the same behaviours for different reasons. For instance, ASD people may fidget/etc as stimming to manage sensory overload, whereas ADHD people may fidget out of excess energy. ASD people may act in socially-inappropriate ways because they don't understand (or care about) the relevant social cues; ADHD people may act in socially-inappropriate ways because they've been distracted out of the context and find it difficult to moderate their interaction. An ASD person might stay up all night reading about some topic because they're kind of obsessed with it; an ADHD person might stay up all night reading about it because hyperfocus kicked in and holy crap it's 8am where did the night go?

ASD people I've known have described it as their magic telepathy helmet being broken and trying to make sense of utterly irrational-seeming other people; I'm ADHD and would describe it as my mental whiteboard being broken and living in a soft rain of post-it notes with every random observation written on them, whether relevant or not.