Time was the only scooters were those used by children - two small wheels and a plank with a broom handle if you built your own !
Now there are some VERY sophisticated scooters indeed - two wheelers in many colors,three wheelers,electric scooters - some even with seats. Quad bikes are of course the continuation of the one person transport - but even this has grown to 2 person scooters and even to sub - aqua scooters ! - That's right - you can even get water scooters either for messing about on the surface or even for underwater exploration.
You can see some of these at

Scooterchoice

Where you can see details of all the good scooters available.

but there are lots more exciting developments too - Mountain Bikes for instance - and there are hundred s of those.
But the firm favourite is still the child's scooter - every fond parent looks dreamy-eyed at their toddler on their first pre-school scooter.
Scooters don't have to cost an arm and a leg - good childrens scooters can be had for as little as $ 19.

Smaller electric scooters are more suitable for people with a lightweight frame and people who are not too tall (under 5 ft 6") Check with your medical advisor if you have problems with leg mobility and they'll advise on the best model for you..
A smaller scooter is definitely cheaper and easier to handle and transport but they are not really as comfortable. Some three wheelers may have a low centre of gravity and these are more stable (but not as good on uneven fground as a four-wheeler).
If you weigh more than 380 pounds or are very tall then you are advised to choose a heavy duty scooter. It may also have difficulty in negotiation kerbstones (an important point as many civil authorities worldwide have not yet woken up to the fact that ramps are essential for some users with mobility problems.
For indoor use a 3-wheeled model will be OK for most users. Three wheelers are more manoeuvrable and are easier to use indoors - they are also a lot lighter.. Smaller scooters usually only have a cruising range of 10 miles or less (DO remember to recharge the battery when you get home - its really important) You can usually also store a lightweight scooter in the trunk of your car - although you will definitely need a trunk lift to get it in and out of the trunk. A Trunk lift is a sort of miniature crane - often electrically driven that lifts your scooter into your car. You'll need to find out if the specific trunk lift will fit your particular car or van. Its usually easier to get your lightweight scooter inside a van rather than a car. Car Manufacturers often have a mobility scheme that gives an allowance towards mobility aids - its best to check with the manufacturer of your car (preferably before purchase as this is a good bargaining tool to get additional discounts.)
Heavy Duty Scooters will give you more legroom as well as handling the larger framed person. If you are mainly using your scooter outdoors the a four-wheeled scooter is much safer and more stable.
Heavy Duty Mobility Scooters usually have a heavier duty battery and this will give you an increased range of travel - sometimes up to 25 or 30 miles depending on model(check on the travel range as its inconvenient to get a flat battery in for instance a shopping mall - its also quite expensive to get a taxi home !) A heavy duty 4-wheeled scooter is usually more stable on slopes or any more difficult land.
Accessories for Electric Scooters.
The most important thing is to get the right seat for your scooter. The more you use your scooter the more you'll appreciate a comfortable supportive seat. These may be available as upgrades before you purchase a scooter. If possible go for a Gel-filled or high quality foam padded. Its vital to avoid pressure sores.
Other accessories available are reachers (to retrieve dropped objects),Baskets (you'll need a basket to carry your shopping home) and other goodies !
The other accessory to purchase ( and I think its really necessary) is a spare battery and battery charger. This will be a great backup for you and one day you'll be very glad you bought one !