All of my posts thus far have been about presenting information or telling a story. This one is more of an opinion and a rant.
Too often, speaking with other physicists, I have had conversations that go like this:
Me: What do you work on?
Them: Condensed matter physics.
Me: Oh yeah? What aspect?
Them: Uhh...materials physics.
Me: Ok, what kind of materials?
Them: Uhhhh...solid state.
Me: What kind of solid state physics?
Them: Uhhhhhhhh systems with many atoms.
This will continue for as long as I have patience, and I will get no information about what the person actually does. If I care enough I can look up their supervisor's research webpage and find out that they actually fire x-rays at superconductors or something like that. I used condensed matter as an example but it's not limited to that. I've had the same conversation go "black holes"..."general relativity"..."collapsed stars."
Physicists, you should not do this. It is annoying, you're selling yourself short, and it's disrespectful to the person asking the question. If the person asking you the question has a degree (or several!) in physics or a related discipline, they'll be able to understand the elevator-description of what you do.
Sometimes I think people give these non-answers because they're embarrassed about what they work on. There is this false premise that there is "real physics" and what they're doing is not it. People working on semiconductors are embarrassed that they're not working on quantum gravity, and the people working on quantum gravity are embarrassed that they're not working on semiconductors. I once had a guy who did simulations of relativistic nuclear collisions, which is like the most physics you can get in three consecutive words, tell me he wasn't doing real physics (although he wouldn't tell me what he actually did!). It's all real physics. No matter what you are working on, you are pushing the boundaries of human knowledge, even if it seems extremely specialized or boringly incremental or removed from reality.
If somebody is asked a question, it is rude not to answer it. In a physics department, it's reasonable that you'll be discussing physics with other people who are well-read in physics. They can handle the truth. If the answer is not detailed enough, the person can ask for more information. If the answer is too detailed, the person can ask for clarification, and try to understand by asking more questions. This type of conversation generally involves two people with differing levels of knowledge on a topic finding a way to meet in the middle. When one side refuses to meet in the middle, either by asking to be spoon-fed or by withholding information, it's not fun.
Now, there is an art to knowing how technical a summary of your work to give. Generally it depends on whether you're talking to someone in the same research sub-field as you, the same science as you, other scientists in different disciplines, or non-scientists. The main thing I'm ranting about is physicists withholding information about their work from other physicists, but I imagine it happens in other fields too.
For my Ph.D. work, I'd generally tell people that I looked at DNA molecules squeezed into very small tubes, to measure how squishy the molecules are. If they asked, I'd tell them how it relates to genetic sequencing technology, and what the relevant physics governing the squishiness of DNA is. If they really wanted to know, I'd talk about screened electrostatic repulsion and conformational degeneracy and the like. But I wouldn't just mumble different permutations of "biophysics...biological physics...physical biology...physics of biological systems..."
So, when someone asks you what you work on. Don't be vague. Be proud.