Block Themes, Classic Themes, Hybrid Themes, Universal Themes. WHAT IS A WORDPRESS THEME?!?!

Описание: It uesd to be WordPress just had themes, but now there are all sorts of types of themes. What are the differences between block, classic, hybrid, and universal themes? AND WHAT IS FULL SITE EDITING?!?! I'll do my very best to make it clear, I promise.