Dealing with many things at once vs. doing many things at once — a difference that lives in your program's structure, not necessarily in the hardware it happens to run on.
"Concurrent" and "parallel" get used interchangeably in casual conversation, and that habit hides a real distinction. Concurrency is about how a program is structured — whether it's designed to have multiple tasks in progress at overlapping times, making progress on each without necessarily finishing one before starting the next. Parallelism is about what the hardware is actually doing at a given moment — whether more than one of those tasks is truly executing during the exact same instant. A single CPU core can be richly concurrent. It can never, on its own, be parallel.