What exactly are "Data sources and sinks and memory format"?

[dntjr8096]

Hi, I am a developer who likes Trino and wants to analyze it.

What exactly are" data sources, sinks, and memory formats" in the sentence "Data sources and sinks that convert the source data to/from the in-memory format expected by the query engine" in the connector description section (p. 47) of the Trino: The Definitive Guide document.

I'm curious how these are implemented in code.