We were given raw data on temperature of coffee cooling over time

What I don't get is why they say investigate power model in the form y=ax^n by to plotting this raw data and log x vs log y?

What is log x is it log to base 10 or lnx? What does it mean?- its is the rate of change of the x variable or something?

Same for Log y?

Then in y=Ae^kx why do we plot x vs log y?

Im sure there is a reason like one is the opposite of the other.. :S

Im just confused? anyone help me?

plz thanks