Website Hosting Resources
Long-term static storage on disk
A website's files, images and scripts, or programs have to be stored permanently on a disk on the server.
The available storage on disk, on each server is limited, so has to be shared between accounts on the web server. So, websites require a limited storage quota, depending on the total number and sizes of these files.
If the server restarts, the data stored on disk is accessible again.
Short-term volatile storage in memory
When a computer accesses data stored in long-term disk storage, it has to load it into memory (often called RAM - random access memory) where it is much more readily available. Memory is particularly important if a website regularly reads files, or a database to dynamically build web pages to display to visitors. These are called dynamic websites. Almost all user editable websites, like WordPress and other content management systems are dynamic.
The memory available to each server is limited, so has to be shared between accounts on the web server. So, websites require a limited memory quota, depending on their processing requirements.
Long-term dynamic, ordered storage on disk
A database is a system which permits the carefully designed ordered storage and retrieval of sorted information in tables and rows, much like a pigeon holed shelf in your office, numbered p.o.boxes, or a spreadsheet in your office software. How the data is arranged in a database depends on the website's application requirements, just like each spreadsheet in your office software is different.
Most modern, dynamically generated websites, like WordPress, require a database in order to function.
If the server restarts, the data stored inside a database is accessible again.
Network traffic, or data transfer is the amount of data transferred, over time, between your website and each visitor to it. Think of traffic like electricity, or water usage.
As with all the other resources, each website hosting account is limited to the amount of network traffic it may consume.