Can anyone simply explain the difference between pre and post? 
In sends I guess Pre is the blue one with “umbrella” to the west
and post the green “umbrella” to the other side. 
What´s normal for vocal? pre or post? 
Testing pro 8.5
Post fader the level of the send will adjust along with the level of the channel. So if you turn down the channel fader completely nothing is being sent either.
Pre Fader the level to the send is set ONLY by the send control. If you turn down the channel fader the send is still active…so you might hear reverb with no source.
Blue is post fade and is the default setting as it’s the one you’ll need for the majority of standard FX duties.
You might use post fade for parallel processing or if you have a specific need to fix the FX level but adjust the original.
Depends what you´re using it for and if you´re talking soleyly about sends or also inserts…