Once map layers have been added to the Map tab, one may want or need to create a map (e.g. PDF). In Pro this is accomplished by creating (inserting) a new Map Layout tab and then adding a Map Frame to the Map Layout. One of great items about Pro is to create multiple map layouts based on one or more map tabs. The map layouts can be different sizes, orientations and even use different map frame shapes like circles or ovals(ellipses).
Guides are often used to “snap” map frames, text boxes, legends, etc to different parts of the map layout.