You can register any name available, but are STRONGLY advised to avoid registering any domain name that conflicts with any company's trademark, as the legitimate trademark owner may have a claim on your domain.

• Domains must be between 3 and 62 characters long, not including the dot and the TLD. For example: impressm.com is 8 characters in length, because .com is not counted.
• The domain name can only consist of letters and/or numbers and hyphens (-), but a hyphen (-) cannot begin or end your domain name.
• Domain names are NOT case sensitive. impressM.com or IMPRESSM.COM or impressem.com are all the same domain.

No two domain names can be exactly the same. If you would like a specific domain and it is already registered, you will need to register some other variation that is available, use a different TLD, or contact the owner and offer to purchase it from them.