Categories content block will list all store categories. Maximum depth of  categories shown is 3 levels.

Title Content block title
Always show
Always show the current level of categories.
Show on parent selected
Show categories of the targeted level, only if a parent category is selected.
Hide unselected
Hide 1st level categories if they are not selected.
Hidden Do not show the targeted category level.
Style Set a style for each category level.
Respect “Top”
When active, only 1st level categories with the option “Top” will be shown.