The top-level domain .fi is part of the hierarchical system of the internet where a domain name functions as an address for a certain service in the internet. The same address may also be presented in a numerical form (IP address) but a domain name, such as traficom.fi, is easier to memorise and to guess. You can get an fi-domain name through a registrar. Registrars also offer email and web hosting as well as name servers.
Legislation on fi-domain names
Fi-domain names are regulated by the Act on Electronic Communications Services (917/2014). Sections concerning domain names are mainly in chapter 21 of the Act.