GVB (Gemeentelijk Vervoers Bedrijf = Municipal Transport Company) runs all bus, tram, underground and ferry connections within Amsterdam.
The main GVB information office can be found just in front of the Amsterdam Central Station.
Another good source of information is the OV service shop, inside the Central Station. This shop has all information of all kinds of public transport in and around Amsterdam.
GVB is one of the remaining public companies - all employees are municipal civil servants. There has been talk of privatization of the municipal transport company in the past, but this never worked out, and at the moment it is not really a topic of discussion.
Tram in front of Amsterdam Central Station
Oostveer (ferry from Azartplein to Amsterdam North)