So if i want my website to be available on the net what do i do
I wanna know
get your domain registered. You domain will be there address that will be entered in the URL bar, by your users. Once you have your domain, you have to host the website on a webserver. normally you will be paying an annual fee for the availability of the website for one year. By registering a domain, you will become the owner of the domain name. your domain would either end with a *.com, *.net, *.org, *.biz, depending on the purposes of your website. You will have to pay a registration fee and an annual renewal fee to maintain the same domain name. After hosting the website, you can distribute or market your domain so that people can access your live website.
buy a hosting and a domain. After park your domain to hosting server you chosen. Then upload your website files to hosting and test the site. Then just add your site to Google.
do I have to pay the when I register
can i use c# as domain ?
Normally it does not have to be really expencive to buy a domain name and hosting... You also could host your website from your own computer so you only haveto buy the domain. But I don't think that would be verry wise, becouse it's not an easy job to host from your own computer and it could give security issus. especially if it's one of the first websites you builded.