All of the programs running on your computer share CPU (processor) time and memory. If you run many programs at once, or if some programs are doing a lot of work, a higher percentage of both of these things will be used.
If the CPU usage is around 100%, this means that your computer is trying to do more work than it has the capacity for. This is usually OK, but it means that programs may slow down a little. Computers tend to use close to 100% of the CPU when they are doing computationally-intensive things like running games.
If the processor is running at 100% for a long time, this could make your computer annoyingly slow. In this case, you should find out which program is using up so much CPU time.
If the memory usage is close to 100%, this can slow things down a lot. This is because the computer will then try to use your hard disk as a temporary memory store, called swap memory. Hard disks are much slower than the system memory.
You can try to free up some system memory by closing some programs. If things get too slow, try restarting the computer.
The memory shown in the Resources tab is system memory (also called RAM). This is used to hold programs temporarily, while they are running on the computer. This is not the same as a hard disk or other kinds of memory, which are used to store files and programs more permanently.
