* Hair Whorls/Crowns: These are natural spiral patterns where hair grows out from a central point on the scalp. They are the most likely thing someone is referring to when they say "hair swirls." Everyone has at least one whorl, usually at the crown of the head. They can be clockwise or counter-clockwise, single or multiple, and their position can affect how hair naturally falls and behaves.
* Cowlicks: These are sections of hair that stand up or lie at an angle different from the surrounding hair. While not exactly a "swirl," a cowlick might appear as a small swirling section of hair.
* Styling Techniques: It's possible the term is used colloquially to describe a way of styling the hair to create a swirling or spiraled effect.
In short, "hair swirls" most likely refers to hair whorls, which are the natural spiral patterns of hair growth on the scalp. If you hear someone use the term, you can ask them for clarification if you're unsure what they mean.