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It is normal and good that most of memory is labeled as cached. This memory contains a copy of files and other data that have been previously accessed and is retained for future use. But the contents of this memory can be quickly discarded and given to any application that needs it. The caching provides a valuable benefit at virtually no cost.
Free memory on the other hand is doing nothing and is a leach on system resources. It is like a company having paid employees doing nothing in the hopes that work will come in for them. Better to have them doing something, anything useful, rather than sitting around doing nothing. Modern operating systems try to keep free memory to an absolute minimum, zero being the optimum value. These are basic concepts that have been a part of modern operating system design for many years.
There are no end of programs available on the Internet that will free up this cached memory and supposedly improve performance.. Their authors either do not understand these basic concepts (more common than you would think) or don't want you to in the hopes you will buy their useless products. Avoid these programs like the plague they are.
