Mathematically:
y = x for 'proportionaly'
As x gets bigger so does y.
e.g V = IR
As the current of a conductor increases do does the voltage (When the resistance is not changing/constant)
y = 1/x for 'inversely proportional'
As x gets bigger, y becomes much smaller.
e.g I = 1/d2
As your distance away from the light-source becomes greater the intensity is much less.