Every website on the internet is “hosted” on a computer somewhere in the world. That means that the files including text and graphics are stored on that computer. Each such computer has an IP address (like 22.214.171.124) stored in the Domain Name System (DNS) and usually associated with a domain name (like platypushost.com.au).
You can host your website on your own computer and be found on the internet provided you register an IP address with two name server addresses (like ns1.yourname.com, ns2.yourname.com) and are prepared to have you computer connected to the internet 24/7.
Domain Name System (DNS)
This stores information such as IP addresses, domain names, name servers (where the IP address is hosted) mail exchange servers.
When choosing a web hosting plan you will find many options for Mb (megabytes) of disk space at various prices. This is just the space required to store your website text, image and database files, web logs and any emails awaiting download. This can be calculated before you chose a hosting plan so that you don’t pay for more than you need but still allow sufficient space for short term expansion.
Data Transfer is sometimes call Traffic or Bandwidth in hosting plans and in that context means the amount of Mb (megabytes) of data transferred in a month. Data is transferred every time a visitor opens a web page, a file is uploaded to the website, or an email is downloaded. So if your website has high resolution images, videos or flash animations, they increase the megabytes of data transferred.
Be aware that your website may have seasonal traffic. e.g. Websites selling toys may get more traffic in the Christmas shopping period, so monthly data transfer needs to be high enough to cover November-December traffic.
Platypus hosting plans do give warnings when limits are about to be exceeded so that you have time to arrange higher limits. There are unlimited resources at appropriate costs.