specialty
Something you are especially good at or known for.
A specialty is something you're particularly good at or focus on, or a specific area someone chooses to concentrate their skills and knowledge. When a doctor chooses pediatrics as her specialty, she's deciding to focus on treating children rather than all types of patients. When a restaurant advertises that pizza is their specialty, they're telling you it's what they make best.
Your specialty might be drawing cartoon characters while your friend's specialty is building with Lego bricks. A bakery might have chocolate croissants as its specialty, the one thing customers come from across town to buy. Scientists, lawyers, engineers, and teachers all develop specialties, becoming experts in one particular area rather than knowing a little about everything.
The word specialize means to develop a specialty. As people advance in their careers, they often specialize, going deeper into one subject instead of broader across many. A general contractor might specialize in restoring old houses. A teacher might specialize in helping students who struggle with reading.
Having a specialty doesn't mean you can't do other things. It just means you've chosen one thing to become really, really good at. When someone asks “What's your specialty?” they're asking what you do best or what you're known for.