Explain the term resource optimization?

Optimization generally means making something to work in a most efficient or most sustainable setting. for example, in case of a human being, you can say that the optimum use of our body is to work for 16 hours and to sleep for 8 hours to be able to have a longer and healthier life. In other words, human body can be optimized to work for 16 hours and sleep for 8 hours. This doesn't mean that humans can't sleep only 5 hours or cant sleep beyond 12 hours, but it is not the most optimum use of our body.
Now applying the same concept to resources, you want to use any resources to their optimum level so that it would neither be over utilized or under utilized, thus maximizing its useful life and cost of maintenance. For example, if in my company I have a commercial printer, I need to decide how many people in the company can access the printer so that it can be used most efficiently. If we let a lot of people to access it, then it might get over used and get frequent repairs, or people might be waiting longer to get their stuff printed, thus wasting their productive time. On the other hand if we let only a few people to use it, then the printer remains idle for longer time and you don't get enough benefit out of it for the money you paid to buy it.
Resources can be optimized not from a monitory sense. there could be other factors that might matter, which needs to be considered while optimizing. i.e. you are optimizing by applying "Constraints". So going back to out printer example, let us say the printer also has a fax machine on it and you don't want every one to access the fax documents received. Now you need to optimize your printer users only among those who could access the fax documents and not to the general public. This process is called Constrained Optimization and it is what would reflect the reality of a situation while optimizing a resource.