Shared web hosting is typically offered by all hosts. In a shared web hosting environment, many clients will share the same server which means that they utilize the same resources on that server. Each client has their own account with their set limits which is set in the package or plan they have chosen. This typically consists of: amount of bandwidth, disk storage space, allowed email accounts, allowed, allowed FTP accounts, script packages, etc. With the shared hosting package the Apache server, Memory and MySQL server are shared. Most times the IP is also shared.
Typically a shared hosting package is a great way to start your endeavor on the internet. Things you should consider however is how large you plan to grow your website. If you have a website that will need quite a bit of system resources, shared options are not always suitable. If someone that is sharing your Apache server has a spike in resources your site could also go down.
Most companies will be able to turn off the resource user fast if they feel that a script is causing the issue. However, this could be bad for your online business or website.
We do recommend shared hosting to the startup company. It is both affordable and a reliable set up for most.