Two different ways of starting a service. Why?

Question

What are the differences between the two following ways or starting something, first being:

/etc/init.d/redis-server start

And second:

/usr/bin/redis-server

I've never really fully understood why which is preferred over the other.

Answer 1

Whatever goes into /etc/init.d is a script that starts a service and may define appropriate level where the script runs - single user mod, multiuser, shutdown; it's not the service itself.

Whatever goes into /usr/bin is the actual server, it is the executable file.

The analogy from windows world would be .exe files vs scheduled services that call those .exe files