[QUOTE=DylanMate;5773843]1: What are "custom firmwares" please explain in full detail be very appreciated!
Custom Firmware is a package firmware when restored, you are already jailbroken. You can preserve your Baseband using CFW. You can add additional sources while building a custom firmware.
2: i have a iphone 4 on 4.1.2 firmware, how would i unteather jailbreak this?
There is no 4.1.2 but 4.2.1 fw, to get untethered jailbreak, currently you need 4.2b3 blob, a Mac to run redsn0w using Monte Jailbreak to get untethered jailbreak.