Web hosting providers provide the following basic services for web servers - anything else can be considered add-on features in theory, although in practice they are rather essential to run a successful Internet business or business website.

A web hosting provider should provide the following as part of the functionality of the web server:

1. Hard Disk Space.
This is what you are actually renting, for all practical purposes. You need hard disk  space on a web server to host your website. A website really consists of a lot of files, much like MSWord documents, or Excel spreadsheets. These files take up hard disk space. The web hosting provider provides you with space so that people around the world who has access to the Internet can access those files on that web server.

The price or hard disks have come down dramatically over the past year or so and it  is not unknown for a hosting provider to make provision for packages from 250Megabytes up to 2000 Megabytes and even more.

How much would you need?
The average web site that just makes use of static HTML pages need about 5 MB to 10  MB of space. If you use a dynamic website where some of your data is stored in a  MySQL database the database will also take up space. These types of sites require  more space and anything between 100MB and 250MB should be enough.

If you are going to store emails on your server you need to add these into your  calculations. Emails can take up a lot of web space very quickly if people send you large files. You will need to monitor the space taken up by Emails very carefully since I've seen individual mailboxes go up to 50 or 60 MBs very quickly.

If you want to host video or audio files on your server, you will have to make provision for quite a lot more disk space. One audio file can easily take up 30 to 40MB.

2. Bandwidth
Bandwidth depends on your traffic. Every visitor to your website will consume bandwidth since this is what they will use when they open any pages on your site.  Once again, if you have video and audio files on your site you will require more bandwidth. A good rule of thumb is to have an allocation of about 100KB (Kilobytes) for every visitor.  This means that 500 visitors per month will consume about 50MB of  bandwidth - although this is only true for an average site with mostly text and a few  pictures. If you have large picture galleries, audio and/or video files you should  rather work on 150KB per visitor or even more. Search engine spiders also consume  bandwidth! You should monitor your bandwidth usage through your CPanel control panel  or your website statistics and make sure that you communicate early enough with your  hosting provider in case you need to purchase more bandwidth to prevent penalties  and/or lockouts.

3. Access to your site
Under this can be counted access to a control panel, such as CPanel, Plesk or Helm, that will help you with setting up of emails, sub-domains, software installations and your MySQL database if you are running dynamic funtionality such as shopping carts,  forums, Content Management Systems etc.

You are also going to need FTP access to upload files to your web server. Without being able to use FTP you will not be able to maintain the content on your site (unless you make use of a Content Management System). FTP access is still required even in that case since you will definitely have occasion to have to upload files such as  pictures, audio, video and other files to your server.

These are the very basic functionality that a web hosting provider should provide!