Simple Examples:
import arcpy
Now you can begin using all the modules, libraries and classes contained within the ArcGIS Python Library.
Let's say we just need the Spatial Analyst libraries. Instead of loading the whole library, just load part of the arcpy library.
from arcpy import sa
The Geo-statistical analyst module
from arcpy import ga
The mapping module
from arcpy import mapping
This can be done for all the python modules, and it allows users to load just what they want.