A school might be said to be lacking resources. In other words, it could be short on School Teachers, Books, Pencils, Funds and so on. All of which are known as resources. In computer terminology resources are Memory, Graphics (Images) and Hardware in general. If a school is short on books the pupils have to share the books. If a computer is short on memory the remaining memory can either be allocated to one program or shared amongst many programs. This is then known as a shared resource.
Shared resources are very common with computers. In schools we prefer the pupils to have one book each. However, when two pupils have to share one book you have a choice. Pupil one can read the whole book before passing it to pupil two or they can simply read the book together. The computer uses the same logic.
One program can be using all of the memory or ten programs can be sharing the memory. All is well. Problems arise when there is not enough memory for each program to have one piece each. For example: If the free memory available is 10 MegaBytes; One program running can use the whole 10 MegaBytes or ten programs running could use 1 MegaByte each. But what happens when a program needs 5 MegaBytes for itself? Well it depends where it is in the queue.
If nine programs are running with 1 MegaByte each and the tenth program wants to use 5 MegaBytes it has to wait until four other programs have finished with their 1 MegaByte. It could start using its 1 MegaByte but it would still have to wait for the other 4 MegaBytes. This might not seem like a problem but more of a waiting game. And this is true if it was that simple. The fact is though programs do not like waiting for memory because it stops their tasks from fully functioning. Some programs might quit if they cannot get the memory. And if they are prepared to wait for memory the time it takes is what makes a program fast or slow. The same with the Internet. If it has a slow connection all downloads (images and text on the website page, the files and so on) will be slower because they are having to wait longer for each Byte to come down the phone line.
The Graphics resources (Graphics Memory on the Graphics Card and the Graphics Card's CPU) are the same. If you have one paint program open it can use all the graphic resources for itself, which means drawing instructions and the editing of a photograph for example will be quicker than if ten paint programs are open and sharing the graphics resources. The graphics resource has the job of drawing your Imagery, Microsoft Word documents and so on, onto the monitor screen by using its graphics memory for editing and display purposes and its cpu to translate drawing instructions.
If you are short on resources sometimes you can do something about it. For example: It might be possible to get a better graphics card with more graphics memory on it. Or a better Webcam. A webcam is a resource in its own right, but if it is too cheap it will use up a lot of the computer's own memory, cpu and graphics resources because it will not have any of its own. The more expensive webcams have their own which means they can display the camera image a lot faster, record video with better quality and so on. As a rule, try and buy a Quality webcam, scanner, printer, anti-virus package and so on as the cheaper varieties tend to use a lot more of the computer's own resources.