You can set the position where you expect the field description to appear. You need to go to:
Click on a field.
Standard Options section
Fill up the Description field.
Set Description Style
You can set the field description to show up at either top or bottom of the field.
You can also select the field description to show up as a tooltip. This allows users to access the description when needed without occupying unnecessary space on the form especially if you have a lengthy description.
In this configuration, the field description will appear as a tooltip when the mouse hovers over the ⓘ icon beside the field title.