When adding the Placester Plugin to a WordPress site, we ask you for your email address so you can create an account. Unlike with some other plugins, we enable you to define a property listing on one WordPress server, then have access to that listing from many other WordPress servers that you control. In order to do this we actually store your listings on our infrastructure and then serve them out to your visitors. Another benefit of this is if your server fails for whatever reason, the listings you created are safe and secure.
If you are familiar with WordPress, you might notice a Properties custom post type and wonder why we need to store listings on our servers rather than in Properties. We use that CPT to store some metadata about the listing, such as address. That metadata is used to ensure that the url for the listing is always the same while retaining the advantage of storing the information on a separate server.