Map frames are containers for maps on your page. They can point to any map or scene in your project. They can even be empty, which most often occurs when creating templates. It is important to note that the extent of the map inside a map frame is unique and independent of any map view that may be open in the project. While the extent is independent, the contents of the map are not. It is just like having another map view open. For example, if you make a selection, those features will be selected in all open views—including any inside the map frame. Likewise, if you turn a layer off in one view, it turns off in all views. Layer properties cannot be set per view. . Clicking the drop-down menu displays a gallery of maps and scenes from the project. The gallery will include all open map views and bookmarks associated with each map. Choosing a view or bookmark will insert a map frame with the map at that extent. Clicking from the gallery adds an empty map frame, which is useful for making templates that can be saved as layout files. Clicking the After you've inserted a map frame, you make changes to its appearance and properties. You can change the map a map frame contains, change the shape of the map frame, add an extent indicator, or add a border, background, or shadow. Extent indicators can be added when there are at least two map frames containing 2D maps on the page. To learn more about adding and working with extent indicators see pane. Through the pane, you have access to basic layer properties and symbology, but to interact with the map and perform tasks such as editing or adding data, you must activate the map frame. For information about working with maps on a layout, see When a map is inside a map frame, it has its own unique view, separate from any other view of that map. You can update the extent by activating the map frame and using the map navigation tools to pan and zoom to the desired extent. By default, there are no constraints on the map extent inside the frame. This means there are no limitations on the type of navigation allowed when the map frame is activated. However, you can lock certain aspects of the view so that they cannot be changed when the map frame is activated. For maps, this includes the extent coordinates, center coordinates, and scale. For scenes, this includes the camera position, center coordinates, and camera height. You can also link one map frame's view to another. When any type of constraint is enabled, navigation while the map frame is activated is limited accordingly. —Sets the exact extent for maps or the camera position for scenes. The map frame reshapes to conform if necessary, and navigation is unavailable when the map frame is activated. —Sets the center point and scale of the map or scene camera height without restricting the extent. Rotation is the only navigation available when the map frame is activated. is locked, the extent of the map or scene is determined by the shape of the map frame. If it's resized, the extent changes, but the center point and scale will not. When is locked, the height and width ratio of the map frame is also locked, and resizing the map frame causes the scale or camera height of the view to change, but the extent will not. The relationship between the map frame and the extent is the key difference between locking If the layout contains more than one map frame, you can enable one-directional links between map frames to tie their views together. Note that when a map and scene are linked, center points are matched, and a best guess is made to link the camera height to scale and visible area on the ground to extent. —Matches the extents of the map frames. The child frame does not resize to match the exact extent of the parent, instead, it adjusts scale or camera height as needed to contain the entire view of the parent frame. All navigation tools are unavailable. —Links the center points of the map frames. If the parent frame is navigated, the child frame pans to keep the center points in sync. When the map frame is activated, zooming is allowed but panning is unavailable. —Links the center point and scale or camera height of two views without restricting the extent. Rotation is the only navigation available when the map frame is activated. is chosen, a drop-down list will appear containing those constraint types. Use this drop-down list to choose one. After you've chosen a constraint type, set the appropriate values. Source.