If you want to write letters on a computer, you're going to need some word-processing software like Microsoft Word. In a similar fashion, if want to use a computer as a communication aid, you're going to need communication software.
What the software does is add all the functionality that helps the communication process - it will contain all the settings and adjustments you need if, for example,you want to use switches as an access method; it will allow you to choose which artificial voice, language, vocabulary and symbol set you want; it will enable you to select and refine any word or phrase prediction that's available - in short, it's the software that makes the computer capable of being an effective communication aid.
The communication software is usually also the 'container' for the third range of products that Speechbubble looks at - the vocabularies, ie the actual on-screen grids of words and symbols.
giving the gift of communication