Ac1dsn0w is a tethered jailbreak for iOS 5 and iOS 5.0.1. This means that you will need to connect your iDevice to a computer with Ac1dsn0w installed to boot tethered when you want to turn the device back on after completely powering it down. Along with Redsn0w and Sn0wbreeze, Ac1dsn0w does the exact same things except that it has a different looking interface. Redsn0w has the most features out of all of the three tools. Sn0wbreeze has a prettier graphical user interface, and Ac1dSn0w is an alternative to the two.

Ac1dsn0w supports the following iOS 5 and iOS 5.0.1 iDevices:
iPhone 3Gs
iPhone 4
iPod Touch 4G
iPad 1

Ac1dsn0w is going to have more features added in the near future. One of the most anticipated is being able to jailbreak a device remotely from anywhere around the world. This means that you can help a friend who is not in the same room as you, jailbreak their device.

Two of the upcoming Ac1dsn0w features are:
Custom Firmware Creation
iRecovery Remote

Ac1dsn0w is currently only available for Mac. It will run on both Mac OS X Lion and also Mac OS X Snow Leopard. A Windows version may be released in the near future.

Download Ac1dsn0w Beta 1 For Mac
Source- pwndevteam