In Blender, what you see can determine what you select. Both wireframe and x-ray view allow you to see and select components on the back side of a mesh. They can be toggled with Shift Z and Alt Z respectively.

Objects and individual components can be hidden and un-hidden with the hotkeys H and Alt H.

Local View, Numberpad / helps you to focus on one object at a time even if it's in the middle of a crowded scene.

Collections can be used to organize objects in the Outliner, which makes it easier to control the visibility of groups of objects as a whole.

Blender has four different icons in the outliner for controlling visibility - the eye, monitor, camera, and checkbox. The eye is good for hiding the object temporarily while the monitor can completely disable it in all viewports. The camera is used for controlling what gets rendered, and the checkbox (only for collections) disables everything at once. If you have a discrepancy between the viewport and your render, always check the visibility icons.