This varies from model to model, but cameras that store the content on a memory card and cameras that rely on cloud services are the most common ones. One of the benefits of cloud storage is that the content is secure even if the camera gets damaged. One of the disadvantages is that cloud services are usually quite expensive. Another disadvantage is that interruptions in the internet connection can affect the camera's ability to upload material to the server. Some surveillance cameras can store the content on external harddrives or NAS.