Mobile Premium Services or 19 SMS Services are information and entertainment services that deliver various forms of content to your mobile phone. These services are created by a content supplier and delivered over your mobile service provider's network. They are called 'Mobile Premium Services' because you buy them using your mobile phone, you receive them on your mobile phone, and you will be charged a premium cost for them.
NOTE: 19 SMS services are more likely than not to be subscription services. Whenever you are buying content using a 19 number - such as a ringtone - you will in all likelihood be signing up to receive more than one and to pay for more than one.