A web server is a computer that is continuously connected to the Internet and has special sever software (most commonly Apache web server) that reads hypertext transfer protocol (HTTP) requests from client side programs (such as web browsers), processes the request and sends either the requested file or resource, or any error codes in an HTTP response. You store your web files on the servers hardrive. A web file is most commonly an HTML file but can also include dynamic content files such as PHP files. Web hosting services will specify the amount of disk space or storage that you get when you use their hosting services. This is a measurement of how much space you are allowed for your files on their hard drive and is usually measured in gigabytes.
Data transfer, or bandwidth is the terms web hosting companies use to refer to how much information you are allowed to send through their server connections each month. If you have a web file that is one megabyte, each time someone downloads or views that file you send one megabyte of information through the connection. Since most web files are relatively small, disk storage and bandwidth are not usually needed in huge amounts. The exceptions apply to sites that get a lot of traffic and contain a lot of large multimedia files such as videos.
Any web hosting service you sign up with should have the ability to process dynamic content. Dynamic content is a web file that contains scripting languages such as php, where code contained in the file will determine what the web server sends in the response to the browser. This allows data and information to be loaded from a database and displayed to the user, or to process user data from form input. This differs from static content such as a plain HTML file that is written and always displayed the same regardless of who views the content, sort of like a painting.
Almost all web hosting services should come equipped with php, MySQL and other popular dynamic content utilities. They should also feature FTP account/ access to allow you to transfer your files to the web server from your development computer, an online control panel that allows you to manage your account and files and tools to measure your bandwidth usage and the disk space that you have used.
Some additional features that are being offered on shared hosting plans include online web page builders that allow you to created web pages in a what you see is what you get (WYSIWYG) interface. This makes it easy for people with little or no understanding of HTML to create quality web sites with ease.
When making your choice between web hosting companies the things that matter most will be the kind of customer and technical support that you receive. As a beginner, being able to get a human on the other end of the phone who knows whats going on well enough to easily guide you through it is an amazing value. If it comes down to a hosting company that offers "unlimited" storage and transfer but isn't there to answer your questions, and one that offers "only" 10 gigabytes of storage but is highly reputable and has great customer support, the obvious choice would be to go with the support.