That’s your actual username. Most people will see ”InsightfulChuck” unless they are mentioning you in a comment or post, or if they view your profile.

It’s used when mentioning a certain user, so that they can see that they’ve been mentioned.
chuckb is your username, so if you add @ to the beginning; @chuckb , it’ll show up in your ”Mentions” section on your page.
Your display name is what everyone can see when you post things. A lot of people (like myself) use their names, while others use nicknames and things like that. Yours is ”InsightfulChuck”, so that’s what people will see when you’re active.
Hope that helped, and if you have any more questions, I’m here.

Thanks Hayden! I’m perplexed about the necessity of displaying both – seems a bit confusing – I guess when I signed up I thought my username was just for login purposes and only my display name would be shown. Now that I see that many people use their real names as display names, I feel like switching my display name to Chuck and using some more creative moniker for my username. But I see no way of changing my username in the profile settings. If I want to change my username, would I have to delete this account and open a new one? Thanks again

No problem!
Yes, you’d have to delete this account and create a new one, which shouldn’t be too much of a hassle. I believe you can do that by going into Settings.