So Many Options - Learn a New One

I recently took a walk in a nearby swamp along the Potomac River, at one point I looked down at the back of my Nikon D5500 and noticed just above my right thumb a button labeled AEL/AEL.  I thought for a second and realized that is automatic exposure lock.  

Automatic exposure today is amazing, but when the scene is complex, with objects in the foreground, depth of field depth of focus can become a real make or break choice. I can freeze or lock automatic exposure with the shutter button, but if I squeeze hard I get a shot I didn't want, and after that one shot, the focus releases.  When I press the AEL button, it is not linked with shutter, I can hold that focus through several exposures.  I learned a new tool, a new option, on a camera I have been carrying for three plus years.  

And there are dozens, maybe hundreds more options.  What I need to do, I find a new one, and spend a couple of weeks using it.  So when the right scene is there, I will know where it is and how it works.  

Do you know what all of those options do on your camera?