I always respond in layers. The first layer is to say I work in computers. If they want to know more, they'll ask. If there is a follow up question that doesn't make it clear they're tech savvy, I'll explain one level deeper. I work on the website for x company, or I help secure your credit card info at such and such back. It doesn't matter if you're front end, back end, dba, network, sysadmin, help desk, etc. Just something that a regular human might recognize as being a thing. Most people don't know what those job titles mean, but they know people must do something to make websites work and secure credit cards. And so on and so forth until it's satisfied their curiosity.

The key thing is knowing that their level of curiosity may not be what you prefer. I've come to terms that people often don't actually care about understanding what I do and would rather just make assumptions about it. If you can't accept that and let it be, you can become a very despondent person. :) And then when you try to correct their misunderstanding, you just make them unhappy too. Everyone loses.

Yep, if they're not actually interested, which is usually the case, you're either going to bore them or insult them because it will come off as bragging.