A domain consists of several parts. In «www.mybusiness.ch», «.ch» is the so-called top-level domain (the country ending for Switzerland), «mybusiness» is the freely chosen name (second-level domain) and «www» is a possible subdomain. For Swiss businesses the «.ch» ending is usually the first choice because it signals proximity and trust; many additionally secure «.com» or «.swiss».
Technically, the Domain Name System (DNS) translates the memorable name into the numeric IP address of the server hosting the website. That is why a domain is always linked to hosting (the website's storage space) and often to email addresses (e.g. info@mybusiness.ch). A domain is registered through a registration office or registrar; the «.ch» ending is managed by the SWITCH foundation.
You don't buy a domain outright but rent it annually. As long as the fee is paid and the domain is renewed, it belongs to you. It is important that the domain is registered in your own name or company, not just the agency's – otherwise switching providers can become complicated. When choosing, the rule is: short, memorable, easy to spell, ideally without hyphens or umlauts.
A «.ch» domain usually costs around CHF 10 to 20 per year in Switzerland, depending on the provider. Some hosting packages include a domain free in the first year. Particularly sought-after, short desired names can, however, cost a multiple of that on the secondary market (without guarantee).