Can someone please explain ROM and how this impacts the Droid?
I am a newbie here so forgive the ignorance..
Traditionally, electronic devices like cell phones would run software that was hardcoded into the device (the ROM being the Read Only Memory that contains it). More recently, devices were made with modifiable software stored in a Flash ROM (mostly read-only, but it can be re-written), so that the manufacturer could easily develop and update it.
In the context of the Droid, a "ROM" refers to a software package which replaces some or all of the normal system software with custom versions. The difference between a "rom" install and a normal application install is that the manufacturer never intended for all of the software to be replaceable by the user - it's a hack.
(Side note: calling it a ROM is actually a bit of a misnomer. A ROM is typically a file containing an image of the exact contents of a flash memory chip. In the case of the droid, it's actually a combination of a linux kernel in an image file and a zip file of software updates. Calling it a ROM just makes it consistent with other devices that still use an image file)
wawa I moved thread so that it will get more exposure. There are some great devs/members etc with A LOT of knowledge of ROMS in this section (hacks) that can give you some great info.
Se7enLC has given you a great explanation already but others may want to add as well.
Just my 2 cents..
You basically would want to flash a Custom ROM just to have features on your phone that it didnt come with.
Some roms will add HTC Sense which is usually only on a HTC Device.
Some will add cusotmizations or tweaks to the UI new icons etc
To get a rom on though you have to root your phone which will give you Admin powers over your phone to do whatever you want.
Think of a ROM as an image of the software...
A complete installable package that contains the version that you are installing, with added tweaks made by the person who put it together.
Similar to this, I can createe a versionb of windows that installed already has numerous applications installed, ready for use. Office, antivirus, etc.