The Transform section of the Details panel allows you to view and edit the transforms - Location, Rotation, and Scale - of selected Actor(s). Also, where applicable, this also contains the settings for Actor Mobility.
Each Transform property has numeric entry fields for the X, Y, and Z axes. You may type precise values directly into these fields to adjust the selected Actors. When more than one Actor is selected and the values of the properties differ, the fields will display Multiple Values. In such cases, entering a number will cause that value to be entered for all selected Actors.
The Rotation fields have the unique ability to be used as sliders. Clicking and dragging on the field allows you to roll the value, increasing or decreasing depending on the distance the mouse is moved.
The Scale fields can also be locked by clicking the Lock scale button. When locked, the ratio of the scale values to each other are maintained when any of the individual values are modified, allowing for uniform scaling.
The transform properties default to relative transformation. This means the transform is relative to the component's parent. Each of the property labels are hyperlinks that can be clicked to toggle between absolute and relative transforms. When using absolute transformations, the transform is relative to the world instead of the parent.
Mobility
The Mobility setting controls whether an Actor will be allowed to move or change in some way during gameplay. This primarily applies to Static Mesh Actors and Light Actors.
See Actor Mobility for more information.