One question which seems to puzzle many of those who encounter
unsupervised learning for the first time is how can anything useful
be achieved when input information is simply poured into a black
box with no provision of any rules as to how this information
should be categorized.
If the information is sorted on the basis of how similar one input
is with another, then we will have accomplished an important step
in condensing the available information by developing a more compact
representation. We can represent this information, and any subsequent
information, in a much reduced fashion.
That can be achieved using Competitive Networks or Self Organized
Maps.