What does a jailbroken iphone mean?

I've read it in the questions many time. But don't know, what it actually is?
n how can one jailbreak an iphone?

Through jailbreaking, you are able to add additional applications to your iphone for free. More info here! :" en.wikipedia.org/wiki/IOS_jailbreaking "

In a nut shell, it allows you to install third party apps and tweaks that can't be found in the App Store. When you jailbreak, it will install another store called Cydia where all of these apps and tweaks can be found. This article sums it up very nicely.

Oh you wouldn't care what it means. Jailbreaking is that kind of techy thing that only matters to people who know how to use the internet.

https://www.google.com/...apple+mean