A layer is the basic building block for map interactions. Each layer can have its legends, attributions, etc.
JEO supports four layer types out-of-the-box:
A map is composed of one or more layers and can be associated with related geolocated posts, that'll be rendered as markers on the map.
Instead of creating a reusable map any time you want to add a map interaction, you can create and configure an inline single-use map via the One-Time Map block for Gutenberg.