Mobile IM (Instant Messaging) - definition
Mobile Instant Messaging is the ability to engage in Instant Messaging services from a mobile handset. Mobile IM allows users to address messages to others using a dynamic address book full of users with their online status updated constantly. That allows anyone participating to know when their "buddies" are available for chat.
The advantage of mobile IM is that messages are sent and received in real-time via mobile handsets on-the-go without a stationary computer. Mobile IM is seen as a natural evolution of the popular SMS service.
Mobile IM is available from some operators or mobile phone manufacturers now, but unfortunately, it is not always possible to use IM services between different operators.
When we state IM in our specs sheet that usually means the phone is equipped with a proprietary IM solution. Those solutions frequently rely on either carrier support or can be used between users with handsets of one and the same make.
Fortunately, popular third-party IM providers such as ICQ, Skype, Google Talk, MSN, AOL, Yahoo, etc. are alleviating the situation by making their own mobile applications allowing mobile phones to engage in Instant Messaging independently of their carrier or mobile phone manufacturer. The only prerequisite is having internet access on the go - over GPRS or 3G.