The way I explain ADHD to my family and friends goes like this:

The brain has all these little separate functions that make up a fully functional mind. Break somebody's brain in the right place and they can lose a very specific ability, like losing the ability to recognize faces, or recognizing faces but losing the ability to feel an emotional connection to the familiar ones! There's a ton of little individual operations that go into making up our complicated behavior in ways we haven't even understood yet.

So one of the specific little functions that a neurotypical person enjoys is a little voice that tells them specific information relevant to this moment. It can say "hey, a lot of time has passed - check the clock" or "hey, you have an appointment coming up in a half hour" or "hey, you're cold, go put on some socks" or "hey, those dishes look out of place. You should clean them up" or even "hey, you are thinking about such and such task, but did you know that task is important right now?". This is called "executive function".

As a person with ADHD, this ability is usually not operating very well. We don't notice the passage of time, we might not notice we're cold, we don't notice that dishes are out of place, we don't remember our appointments at relevant times, we can actually think about a task without realizing it's important right now, and our brain generally doesn't automatically tell us details that are relevant to decision making. Executive function isn't giving us these updates.

Another feature of the brain is the chemical dopamine, which is the chemical that motivates us to take action. When you see something new and amazing on the internet and feel compelled to take action and go looking for more, that's the dopamine kicking in.

Neurotypical people get dopamine hits for everyday tasks and responsibilities because their executive function is saying "hey, this task is important right now - here's some dopamine! Go do the thing!" This doesn't usually occur in the ADHD brain so it's hard to get motivated for chores and stuff. But we do still get the dopamine hit for amazing / novel stuff, so we can easily be distracted from the stuff that doesn't excite us!

So the results can be confusing to somebody trying to understand ADHD behavior. It can look like we're just choosing to do the things we like and ignore the things we don't, but it isn't as much of a choice as you might think when there's no dopamine available for mundane tasks. "Attention Deficit" makes it sound like we won't ever be able to concentrate, but we can actually hyper focus on something we like for hours. And that's because the novel / exciting thing we like gave us the dopamine to follow through AND the executive function isn't reminding us about how much time has passed or our other responsibilities or the needs of others.

And let it be known that we WANT to be responsible and we want to do what's right and we want to hold up our end of the bargain, and we want to keep appointments...but we need some help.

To do mundane stuff, we need external stimuli, like alarms and notes and reminders and people. People are especially important because we're still sensitive to the needs and wants and expectations of others when they're present. We can just agree on a task or a goal with another person and as long as they're in the room, we can just motor on through and complete the task! We call it "body doubling". I've discovered that I actually really enjoy doing dishes by hand as long as me and another person are working on cleaning up together! I want to be helpful, and I want to collaborate, and I want someone with a working hippocampus to confirm that I'm doing the right thing right now.

I hope that's helpful.