A website consists of one or many Web pages sharing a common a common part of the URL called a domain name. For example the URL of this page is http://www.the-online-world.com/website-introduction-101 . As you may notice, all other web pages on this website share a common part in the URL ‘www.the-online-world.com’. This part of the URL comprises the domain name. All the Web pages of a website share the domain name but have different and unique to themselves the rest part of the URL.
Home Page:
Also called the main page or the index page of a website, it is the page that automatically loads when only the domain name of the website is accessed. Usually it is actually the main page of the website introducing and setting a structure for rest of the web pages on the website. Web pages are structured using a network of hyperlinks on a website starting from the home page.
Sub-domains:
Sub-domains in the domain name system (DNS) hierarchy are defined as simply being part of a larger domain. Sub-domains are denoted by putting the sub-domain name before its parent domain name separated by a dot. For example, in www.answers.yahoo.com , answers is a sub-domain of the main domain name Yahoo. Yahoo, however, in itself is a sub-domain of the com domain, which is referred to as a top level domain or TLD. In theory, this hierarchy of domains and sub domains can go 127 levels deep. Sub-domains are generally used by organizations to assign a separate unique name to a totally distinct part of its website. This helps in creating a definite brand value for that part while also maintaining the relationship with the main domain.