What does it mean to jailbreak a iphone?

What does it mean to "jailbreak" a iphone?

Basically installing your own OS(usually a cracked version of IOS)

Jailbreak means to have your phone with customization
I recommend Jailbreaking (my iphone is jailbroken)
It allows you to customize phone icons (apps)
text (font) cool tweaks

just watch it on youtube and stuff its 100 percent safee.

Jail breaking an iPhone allows you to download and use many apps from 3rd party app developers. It does however void any warranties and if damaged the apple stores won't even touch it. That being said it can be reversed if necessary

Changing your phone to remove all security things that limit developers. Warning, doing it will remove warranties and is not allowed by apple.

Basically its hacking it, without getting too complicated.

It lets you use Cydia which is an app store for things that Apple won't let on their app store.

Jailbreaking a smartphone means installing software that uses security holes in the phone to bypass the normal security protection of the phone, allowing you to do things that the manufacturer doesn't want you to do. Since it requires a compromise of security, it also opens the door to viruses and such, even though these normally don't affect smartphones that haven't been jailbroken. In some cases, jailbreaking also destabilizes the phone (causing crashes or freezes) or breaks apps.

In general, if you don't know what jailbreaking is, you definitely should not attempt it. I never jailbreak, because I want a phone that works, not a phone that crashes, freezes, stops doing what it's supposed to do, or gets infected with viruses.