Jailbreaking my iPhone, what would happen?

•If I jailbreak my iPhone, will I still have my pictures, contacts, apps and text messages.
•If I jailbreak my iPhone, can I take off the jailbreak and will I get my stuff back if I lose it?
•If I jailbreak my iPhone, can i switch back to my regular iOS version?
•What the difference between untethered and tethered.
Who ever answers all of those questions will get 10 points.

Yes you will lose nothing and you can get back by restoring it with itunes.

•If I jailbreak my iPhone, will I still have my pictures, contacts, apps and text messages.
Backup every thing up, and NOTHING happens to your pictures, contacts, apps and text messages.

•If I jailbreak my iPhone, can I take off the jailbreak and will I get my stuff back if I lose it?
Again if you back everything up FIRST or BEFORE you want to Jailbreak, everything will be fine.

•If I jailbreak my iPhone, can i switch back to my regular iOS version?
Yes if you use the correct method to un-jailbreak your phone, putting things back to stock iOS will be a piece of cake.

•What the difference between untethered and tethered.
Tethered methods need a computer to jailbreak, with the iPhone connected by the data cable.

Untethered methods, use an app that is installed on the phone to jailbreak it. But with All jailbreaking methods, you will want to backup EVERYTHING you don't want to lose FIRST. Backup to your computer and then also backup to the iCloud. This way you have two backups to turn to if something goes wrong.

Nope, you will not lose anything.
You don't need to worry about losing your stuff
You can take off the Jailbreak by restoring it on Itunes
If you update your iOS you will lose your jailbreak.

The difference between Untethered is that when you completly shut it down, the jailbreak will be gone
(you will have to jailbreak it again. It takes a couple minutes.)
and Tethered is when you shut down your Iphone/Ipod the jailbreak will still be there.