If you want to see all the 'Organisations' that you have on your database you can use the 'Organisation' filter to view these contacts - this is useful particularly in a Business to Business environment - as shown below: 



'Organisation' mode can also be used to view all contacts at that organisation and keep all communication with those contacts within the 'company' record rather than in each of the individual people's records at the company. 


The screenshot below shows the individual contacts within the 'company' record: 



If you go to the History section you will see all history combined across all contacts stored inside the 'company' record as shown below: