At this point you need a way to access your collection of sites and sub sites via a web browser.
A web application is the logical component:
- It has a Host Header (URL), e.g. http://intranet.
- It stores data inside one or more associated content databases.

A web application can have several site collections all accessed by a host header:
- http://intranet
- http://intranet/sites/hr
- http://intranet/sites/operations
The decision to store information in one site collection or different site collections is a matter of logical architecture which isn’t done in this document.
Web Server
A web server is a server where a set of services are running to publish web sites to the internet or intranet. Of course a web server can publish more than one web site:

Multiple SharePoint servers are grouped to a SharePoint server farm.
Server Farm
While the front-end web server publishes information to the Internet or Intranet the database server is required to store configuration data and content.

A server farm can have multiple front-end and database servers.