Thank You Scary Alien, so if I am understanding if my unrooted Eris is running 2.1. Would it possible to flash a 2.2 ROM so I can take advantage of WIFI tethering ? So all the ROMs out there how will I know which version Android they are for ?
You actually do not need 2.2 to get WiFi tethering; there are WiFi tethering apps for 2.1, and, in fact, I think that most of the root 2.1 ROMs include a WiFi tethering app. For example, the great xtrROM 4.0.6.1 includes both wired and wireless tethering apps.
While it is true that FroYo (i.e., 2.2) includes native support for WiFi tethering that 2.1 did not, I do believe that none of the 2.2 ROMs for the Eris right now support that built-in tethering feature - they use the same third party apps that 2.1 ROMs do.
The best place (IMHO) to find ROMs for the Eris is at
xda-developers Eris development forum. Look for the threads that have
[ROM] in the title; the first post of each of these threads will tell you which Android version that they are, whether they include Sense or are vanilla Android, and most of the features. A sort of glossary of terms you might find:
apps2sd: includes support for installing applications on your SD card. Read the post carefully to see how it is implemented, and note that all Froyo ROMs support apps2sd by default
JIT: Just In Time compiling. The ROM uses this technology to speed the java interpreter used when running applications. Again, a default feature of Froyo ROMs. Note that some older apps do not run well in JIT-enabled ROMs; Pandora used to have an issue with JIT, though perhaps that is no longer the case.
OC: the ROM supports overclocking of the CPU, letting the phone run the CPU faster than its default 528 MHz clock speed
LWP: the ROM support live wallpapers
AOSP: Android Open Source Project. Rather than using the customized Android build that HTC used on the Eris, these ROMs are built using (or based on) vanilla Android source code
JulyOTA: For either Sense based 2.1 ROMs, or ROMs with most of the HTC Sense customizations. The ROM includes the features that HTC included in the July Over The Air update that was delivered to stock Erises
Hopefully, any other acronym that you read is obvious.