Definition                                                  
A business cluster is a geographic concentration of interconnected businesses, suppliers, and associated institutions (e.g. universities, standardizing units, business associations, and financial institutions) in a particular field. In a cluster, companies compete with each other, but at the same time cooperate in certain fields, and because of that derive shared advantage. /Michael E. Porter/ 

Cluster – a source of trade development
A cluster is above all a cooperation of people from different organizations. Interconnections existing between them enable effective information flow and developing a joint knowledge base then used by the whole cluster. Concentration of objects from one field on the same geographic area also influences their specialization and because of that drives their development. A cluster is a good place to attract investors, valuable employees and new companies.

Examples of clusters and their specialization                                      
The best example of a cluster is the Silicon Valley in the USA, where on a territory of 300 square miles operate several thousands of technology companies, employing over a million of top-class specialists. It’s being powered by one of the most renowned colleges in the world – Stanford University. It’s strongly connected with new  technology sector and local business – it is its research base and it educates its new personnel. In Poland the biggest clustering initiatives are i.a.: Łódzki Klaster Medialny, Plastikowa Dolina, Tarnowski Klaster Przemysłowy, Wielkopolski Klaster Meblarski, Klaster Piwny.

Developing image of the region
The source of trade development is a cluster and its contact network, and not an individual company. The mobility of employees and developed this way social and business contact networks enable effective knowledge and information flow. People, who change companies and projects, constitute a kind of  „super-organization” that drives  boom for products and services from a particular branch, and creates a desirable image of a region, in which the cluster operates.