Deprecated code is code that is no longer included in the language specifications. Generally this happens because it is replaced with more accessible or efficient alternatives.
Stands for Domain Name Service (alternately Domain Name System or Domain Name Server). Basically, it’s the thing that converts IP addresses into domain names. DNS servers are provided with the IP address of your web server when you assign your domain name to those servers. In turn, when someone types your domain name into their web browser, those DNS servers translate the domain name to the IP address and point the browser to the correct web server.
The domain is the name by which a website is identified. The domain is associated with an IP address. Domains can be purchased with any combination of letters, hyphens (-), and numbers (though it can’t start with a hyphen). Depending on the extension (.com, .net, .org, etc.), a domain can be anywhere up to 26 to 63 characters long.