There's no denying that mobile phones are consistently developing in terms of technology, features, usability and function. The advancement in mobile phone handsets is so drastic that a whole new breed of phones are on the market, these cutting edge multi-taskers are often referred to as 'smartphones'. There is no universal rule for handsets to be considered amongst this elite category, but the underlying principle behind a smartphone is that it offers functionality and applications which reside more in the parameters of computers than conventional mobile phones.
The origin of the smartphone can be traced back as early as 1992 to IBM's 'Simon' handset. Incredibly for a model of its time, Simon featured a calendar, games, email support, fax capabilities and a touch screen. Although the handset would be more at the entry level end of mobile phones in the modern day, 18 years ago the technology was far beyond that of any competitors. From 1996 the smartphone market was truly established with Nokia's entry into the arena courtesy of the Nokia Communicator line, which consisted of models which were essentially an amalgamation of mobile phone and PDA. Since the release of the Communicator series many other manufacturers have become involved in the market.
The smartphone 'badge' is time subjective in that a handset which featured email functions at the very beginning of the 21st Century would have been considered a smartphone at the time but would not necessarily be today off the back of that function alone. Features which tend to render a handset amongst this elite class in the modern day are more along the lines of VGA connectors, built in keyboard, Wi-Fi and accelerometer technology.
Amongst different communities however the definition of a smartphone is more specific than just a handset which offers technologically advanced features. In the realm of developers for instance to some it refers to phones which run a complete operating system whilst others may well grant the status only to units which run an autonomous operating system which provides a standardised interface for application developers.
Due to the absence of any solid rule which officially makes a phone a smartphone, the term (like many others) is most widely used for marketing purposes as opposed to technical descriptions. As a result of this, handset purchasing decisions should not be based purely upon a particular phone being referred to as a smartphone: this is does not mean that it is superior to a handset which does not utilise the term in its marketing activity, or is not listed as a smartphone in a review or product description.
In short, 'smartphone' has that many different definitions as to mean very little to the general end consumer, not least in that its specific meanings in different circles can easily lead to ambiguity.