A whole lot. Too much to cover in one post in any kind of detail.

A modern relational database management system (RDBMS) is a highly optimized beast. How it accesses storage is very carefully considered. It has a whole mini language for defining relations between data. There are tools for debugging specific queries to make them faster. They index data with tradeoffs between read and write speeds. There are sophisticated locking mechanisms so multiple users can read and write at the same time. They have transactions where many alterations can be packed up together and written efficiently at once. Those transactional alterations are atomic, meaning there are guarantees that all of them happen or none of them happen. The entire thing is based on set theory, and it has survived attacks by many other pretenders to the throne for decades.

And if you’re using Oracle, you can get all that while paying a highly optimized pricing model set up by the best financial advisors Larry Ellison can find to maximize value extraction from your company.