# Explanation

<!-- diataxis: explanation -->

Concepts, architecture, and design decisions behind plone.pgcatalog.
Read these to deepen your understanding of how and why the system works the way it does.

```{toctree}
---
maxdepth: 2
titlesonly: true
---
architecture
why-postgresql
fulltext-search
tika-extraction
performance
security
bm25-design
addon-integrations
```
