The Presto website (and other docs) talk about "interactive queries" on Presto. What is an "interactive query"? From the Presto Website: "Facebook uses Presto for interactive queries against several internal data stores, including their 300PB data warehouse."
An interactive query system is basically a user interface that translates the input from the user into SQL queries. These are then sent to Presto, which processes the queries and gets the data and sends it back to the user interface.
The UI then renders the output, which is typically NOT just a simple table of numbers and text, but rather a complex chart, a diagram or some other powerful visualization.
The users expects to be able to e.g. update one criteria and get the updated chart or visualization in near real time, just like you expect on any application typically. Even if the creation of this analysis involves LOTS of data to be processed.
Presto can do that since it can query massive distributed object storage systems like HDFS and many other cloud storage systems, as well as RDBMSs and so on. And it can be set up to have a huge cluster of workers that query the source in parallel and therefore process massive amounts of data for analysis, and still be fast enough for the user expectations.
A typical application to use for the visualization is Apache Superset. You just hook up Presto to it via the JDBC driver. Presto has to be configured to point at the underlying data sources and you are ready to go.