The Highlight button allows users to identify selected objects in the model by colouring the object pink.
Note: You may need to set the Toggle Wireframe/Rendered option to wireframe if the object selected is not on the outer face of the model (for example, an internal partition).
Highlighted Internal wall in Wireframe view.
Highlighted Window in Rendered view
If a higher level is selected in the model tree, then all subordinate objects will also be selected and highlighted.
Multiple Windows highlighted in Rendered View