It’s written in Rust with a SQLite database, providing a graph with the connections between your data, and using a schema to describe how elements are structured. It organizes content by types of items (what kind of properties does a person/email/photo have), relations between items (E.g. “John is my brother”) and relations between types (a blog is also a website).
The Pod provides an HTTP interface to access to your data from the client or a plugin. You can check out the HTTP API.
You can download the source code to host your Pod on your own hardware.