SMS stands for Short Message Service and is commonly know as text messaging.

It's great for sending quick little messages to friends' phones and normally cheaper than a mobile phone call.

So, next time you're running late you can just key in "On my way!"

SMSing

On nearly all mobile phones, SMS allows you to send short written messages of up to 160 characters or about 25 words.

Over one billion text messages are sent each month. Some of the more modern phones allow simple pictures to be sent within a text message.

In more recent times many publishers, online providers and games companies have started to launch alert and gaming services.

Typing them in

In older phones you write the letters by pressing the key repeatedly. So, if you press 2 once, it writes an 'A', if you press it twice a 'B' and three times a 'C'.

Nowadays many phones have dictionaries inside them and guess the word you want to write even when you just press the key once. It's great - because it saves a lot of time and effort!

Text Message Alerts

Alert services give information such as updates on the latest news headlines, sport scores and share prices. So they could be a newsflash or a football goal alert!

Other alerts might be your daily horoscope and information services covering everything from music news to the latest stock market quotes.

Normally you will 'sign up' to receive such a service by dialling a premium rate telephone number to cover the cost to the company of sending you the messages. Or, by sending a simple text message to a mobile number with a keyword such as 'START'.

If you have not paid for the messages as part of the registration you will probably be charged for each text alert message you receive.

So, it's really important to remember that nothing in this world is for free and to read all the small print.