The Outlined is a bit of a different animal from the 3D view, and the click behavior in one isn't the same as the click behavior in the other, and the Outliner can indicate different object selected than the 3D view. Selecting the white triangle will take you to that object and put you into Edit mode.
Select the white triangle to the right of the name to enter Edit Mode for an object. Select the yellow triangle to the left of the name to select that object in the Object mode. The yellow triangles to the right of any name are the child objects, and you can select those by clicking them but it's harder to remember the exact order so usually people expand the object to see the children. It gets confusing when you click the empty space to either side of an item in the outliner, because that only highlights the name but doesn't select it in any way. To select a highlighted object(s), right-click and choose Select. The highlighting option is available because it makes it easier to select multiple objects at the same time (using B to make a box, or shift-clicking). The highlighting ability is redundant and it would be better for Blender to immediately select in Object mode when you highlight (which is similar how Windows and most other software works), but that's the way Blender 2.79 does it.