What does it mean to "optimise" a compiler? When might it be helpful for a computer to use one of these? When might it be considered rude to use a tool like this?

Why is it that we are in such desperate need of effective compilers? If you were a programmer, what type of software would you develop for one of them if you were given the opportunity? Nothing even somewhat similar to this could ever be considered useless, right?

Could you please list the top six reasons why you are interested in learning about compilers?

What does it mean to "optimise compilers" exactly? When would you utilise one of these as a software developer? When does the use of a technology like this make no sense at all?