C programming

I can't seem to wrap my head around this concept of "value and effect" when dealing with expressions and assignment in C programming:

We're asked questions like:

1. What is the value and effect of the following expression? Answer this in the form of Value: , and Effect:

   Example of this is

   float y: Value: 1.3333

   y = 4.0/3; Effect: 1.3333 ---> y

Some I've made up:

Int z = 4; Value:________?

z++; Effect:________?

Another one:

Int z = 4; Value: ________?

++z; Effect:________?

If someone could explain this in detail, I'd really appreciate it! Thank you!