If you want to drive a car you will need to take out car insurance. If you want to ride a motorbike you will need to take out motorcycle insurance instead. It works in much the same way, and is there to protect you and other people if you are involved in an accident.
Do motorcycles fall into different insurance groups?
Yes they do. Strictly speaking the more powerful and the more expensive your motorcycle is, the more expensive it will be to insure. To this end it is worth considering what you can afford by way of insurance if you have not yet bought a motorcycle. You may find you are restricted to the bikes at the cheaper and less powerful end of the market, at least until you have shown you are a responsible rider who is not likely to be involved in an accident.
Are there different forms of policies available for motorcycle insurance?
Yes there are, and it is worth considering which form would suit you best. For example third party fire and theft is the cheaper option of the two, the other one being comprehensive insurance. The main differences are much the same as would be applicable to car insurance. If your bike incurs damage in an accident that is your fault, repairs would be covered by comprehensive insurance but not by third party fire and theft insurance.
Of course it is always wise to read the policy details carefully for any quotation you receive. They can differ markedly and no two policies are likely to be exactly the same. This also applies to the premiums attached to each policy. It is wise to compare policies offered by different insurers so you can be certain of getting the best insurance cover for the lowest possible premium.