what actually happens, if you are typing in your web browser: ‘http://www.star-sushi.com’, for example? initially, the browsers (such as microsoft internet explorer, the mozilla firefox, opera, et cetera) don’t know anything about this alphabet soup. so it has to ask somebody. this is the role of the dns servers. only these important devices translate the letter combination ‘www.star-sushi.com’ into a computer understandable language, namely the ip address. this case here ends up finally with 82.98.86.180. only this raw number the browser understands, and opens the desired site. usually.
but if so, then the dns server knows everything about me: when and what I’m surfing in the internet, when and what I'm looking for or when and to whom I send an e-mail?
yes, exactly just so! all of that. and it knows very much more about you. on the one hand and not to underestimate: you are mostly personally known, because of you receive your isp's dns servers inclusive 'in the box' almost all times you connect to the internet.
you can easily check this by opening a command prompt and typing in: ‘nslookup sigfm.de'. you will receive as a result not only the ip address behind the domain ‘sigfm.de' but also this one of the providing dns server. actually, yet prior to the requested answer. it shows something like: ‘server 208.67.222.222' and ‘Address: 208.67.222.222#53'. now enter the command: ‘nslookup displayed-ip address' and you will receive as a result the fqdn of your currently providing name server. this figure shows the process. to find out which ip address is behind the domain ‘sigfm.de ', the vatican was inquired. now in addition, there is knowledge about the questioner there as follows:

1 the requesting ip, what means yours,
2 the time of the request,
3 what was searched for, and much more.

well now, frightened? read more here...