What does jailbreaking your iPad do?

[Sel Rentali]

My iPad is going to come in the mail on Monday, and I heard about the Spirit (Jailbreak) and I was wondering , what exactly does it do & does it make ALL apps free? Will iMovie be available for free?
Thank you any info is good!
Is it going to harm my iPad or change it in a bad way? (like slow it down)?

[classicsat]

It lets you modify the OS at the level Apple does not want users to, and lets you run applications/software not authorized by Apple.

What it is not, and I stress this point, an entitlement to use pay for software and content without paying. The software is still copyrighted, and with that, the authors still have the right to get paid. What people most likely mean when they say you can get free software, is that the software is somehow pirated. Yes, it can be the case that some software is intentionally free on the "free" software network.

[A F]

It let's you use 3rd party apps that aren't in the normal AppStore....some normal apps will be free... But it does diminish your warranty so be aware if that.... I would say keep your iPad normal for a week to decide weather or not you really want to jailbreak....