They have solid state storage (high endurance solid state storage) so it is permanent and not removable or swappable.
There is a competitor that uses SD cards. Each vendor has their mktg pros/cons for SD vs. SSD, and each one will tell you why they chose one over the other. We chose Meraki and I think it's better to have SSD.
Note: I should add that the SD implementation we evaluated did not allow for access to the SD card. So even though the camera has SD, you still wouldn't be able to swap out on your own, or access the files.