Long term scheduler:
The term long term is based on the fact that this scheduler has a long term impact on the efficiency of the system. How many processes need to be pushed to ready queue define the degree of mutltiprogramming. Consider if the LTS pushes only high IO bound processes, this will lead to a lot of waiting time and hence the CPU will be idle for most of the time, on the other hand if LTS pushes high CPU bound processes it will lead to starvation of processes as one process will require a lot of CPU time. Whatever may be the case it is certain that LTS has a long term inpact onto the effinciency cz which ever processes are pushed in ready they have to travel through the process states.
Short term scheduler, similarly, has a short impact on CPU eff. As it can impact as long as the scheduled processes executes, and also deals with only two states, i.e. ready and run.
Medium term scheduler deal with suspended processes from ready queue or from wait, which process to suspend when a high priority process arrvies is handled by it.