When you're looking to buy an iRobot Roomba, something that can be confusing is all the features. Some of them are self-explanatory, but there are a lot of others that aren't so obvious. I was looking at the features of the Roombas recently and compiled this list, which I think is pretty complete. There are a few of these features that almost all of the robots have. The most obvious is that they are all vacuum cleaners. All of them have filters to trap allergens and are equipped with cliff sensors so that they won't take a spill down your stairs. Roombas are also not built to use dust bags like most vacuums. They all have chambers that you empty out.

So then here are the Roomba features that aren't built into all the robots.

Spot Mode - When you want a Roomba to clean up just a small area of floor, you can tell it to do so. When you put it down on the floor, you press the botton on the top of the robot labeled "Spot Mode" and then the Roomba will concentrate on that area.

Max Mode - This is almost the opposite of Spot Mode. Usually a Roomba will decide that it has covered the entire room and vacuumed sufficiently. Then it will stop and either move on to another room (using a lighthouse - see below) or will return to its base. When you set your Roomba on Max Mode, it will clean and clean and clean a room until it only has enough battery left to make it back to the charger base.

Fast Charging - These Roombas are able to charge in three hours. The standard charging time for most other Roombas is seven. This is probably a good thing if you have a large house and want to use the Roomba in a couple different areas.

Dirt Detection - Roombas that are equipped to do this use a light to detect areas of the floor that are especially dirty. They will then signal that they found a place with a blue light and circle around and around on it until it decides that the area is clean.

Self-Charging Base Compatible - Here's another one that is very common and most of the robots on sale now do this. Basically, it means that when the vacuum cleaner is done with a room, or if it is running low on power, it will zip onto the charging base.

On-Board Scheduling - Wouldn't it be nice to be able to have the robot vacuum your house or apartment while you're gone? With on-board scheduling, you can choose times for your Roomba to activate and vacuum your home.

Improved Navigation and Floor Coverage - These Roombas have the newest firmware and cover more ground more effectively.

High Capacity Sweeper Bin - I've read in a lot of places that this is a must-have feature for people who have pets, and is almost completely necessary for people who have very hairy pets and/or kids. The larger bin means that the robot can vacuum more area before it needs to be emptied.

Easier Maintenance - These robots have been designed with care and cleaning in mind. You do have to clean the brushes and filters on the Roomba from time to time. Roombas with this feature are easier to maintain, and also provide helpful information on how to do so.

Wireless Control - This is the coolest feature!!! You can remote control the Roomba to make it zip around the room. Clean up areas you want cleaned or menace your cat or dog! Very cool.

Virtual Wall - Use these to keep your Roomba from going places you don't want it to. Some people use these to keep Roombas from going places they get stuck (like where there are lots of cords.) You can also use them to block doorways.

Lighthouse Technology - A lighthouse is like a Virtual Wall (see above) except that you use it to control when your Roomba can move on to another room. While the Roomba is vacuuming a room, the lighthouse prevents it from going into the next room. Then the Roomba finishes the room it's working on, the Lighthouse lets the Roomba through and then "shuts the door" so that the Roomba doesn't go back to the room it just finished. Very cool.

Voice Demonstration - These Roombas have a voice which tells you useful information, such are usage instruction and also if the Roomba is stuck or needs to be emptied.

Light Touch Bumpers - Here's an obvious one. These Roombas have special sensors built into them so that they know they are approaching a wall of piece of furniture. When they approach something, they slow down so that they hit it very softly. Frankly, the Roombas hit everything very softly already, but this turns it up a notch.

Well, that's about it. I'm sure that iRobot is working on more features as you read this. Roombas are pretty cool.