Beginner question about 2-speed 4X4 Switch 2018 Cherokee Trailhawk
 

I hope this is the right forum. If not just let me know where I should be. Thanks! Incidentally I don't know how to decipher the two-letter codes like "XJ" or "KL". How do I know which one I have?
I just bought a used 2018 Cherokee Trailhawk yesterday and this is my first Jeep, other than the ones I drove and rode in in the Army. I have been trying to find an explanation that makes sense for the "Selec-Terrain" buttons. The two selections on the left make sense. The top one is the 4WD Low and the bottom appears to be the Rear Lock, which locks the rear axle so that both rear wheels are always getting power. But the two buttons on the right that look like ducks aren't clear to me. When and why and how would you use them and what do they do?
Thanks for your patience with a newbie and for your help.

XJ= 84 to 01 amazing box on wheels

KL= 2014 to present. Not a box on wheels

those arent ducks that's a speedometer over a Jeep. The top one is hill decent control and the bottom one is I believe crawl control control. Think of it as off road cruise control

Thanks for the reply. Sure look like ducks to me. Curious how you operate the "off road cruise control". In other words how do you set the speed etc. The manual sure doesn't seem very clear on it to me. Thanks again!

Google can help you figure a lot of these things out. I dont have a KL and have never driven one so the things I'm posting here are from internet searches

This link includes a video

http://blog.autostarusa.com/selec-speed-control/

I searched and watched several videos before posting this question. Never saw this video. It was not a great video as far as showing the real purpose and operation because even the driver and apparently the guy taking the video did not even know the ins and outs of operating it. I guess I'll have to make my own when I get to Factory Butte in central Utah next month. By then I'll figure it out and make a much better video than any I have seen so far.

Thanks for linking me to this one and for the bullet points on it. Very helpful when put together with the manual and the vague and confusing instructions there.

The 4x4 low button puts the vehicle in 4x4 low just like a part time 4x4 system so don't use it on the road or high traction surfaces.
The Rear locker is a selectable rear electronic locking diff, it can only be enabled in 4-low.

The other 2 buttons you are reffering to are
1. Hill decent control, which available in 4-low controls your speed down hill (you can control how fast)
2. Selec Speed control, which is available in 4-low is basically offroad cruise control, you set it at a certain speed and it will crawl along at that speed.