Logs and exponents of the same base are inverse functions of one another. Imagine an exponent machine that takes x as an input as produces ax as an output. A Log machine would take that ax as an input and produce the original x back as the output. So the log "undoes" what the exponent does.
x -->[Exponent] --> ax -->[ Loga ] --> x loga(ax) = x
(base a) (base a)
It work the other way as well - the Exponent function undoes what the Log function does to x:
x -->[ Loga ] --> loga(x) -->[Exponent ] --> x aloga(x) = x
(base a) (base a)
(base a) (base a)
To see representative graphs, click on the link below:
http://www.wyzant.com/resources/files/290591/log_and_exponent_graphs
For a good general overview of the relation of exponents and logs, click on the link below:
http://www.purplemath.com/modules/logs.htm