Patents - what we are talking about
The basic idea of the patent system is to advance innovation by guaranteeing the exclusive commercialisation to the inventor and requiering her to publish the invention. A patent can be defined generally as
'... a set of exclusive rights granted by a state to a patentee (the inventor or assignee) for a fixed period of time in exchange for the regulated, public disclosure of certain details of a device, method, process or composition of matter (substance) (known as an invention) which is new, inventive, and useful or industrially applicable.' (Wikipedia)
To be patentable, the invention must be a technical one, it must be new and it must be an inventive step which is susceptible of industrial application. It is therefore important that the invention is not self-evident and does not arise from the state of the art. Once a patent is granted by the EPO, it is valid for 20 years.
Patents vs. copyright
Patents are granted for certain avenues of approach and not for products. Creations - like books, songs or software - are copyright-protected from the moment of their production whereas patents must be applied after the invention. Because copyright is at everybody's disposal it is quite fair in contrast to patents, where the strongest player - the one who owns the most patents - prevails. Software patents do not concern certain programs like 'Microsoft Word' because they are protected by copyright anyway, but they refer to combinations of algorithms which are used in this programs.