You should KNOW 

1. That  log_a x is "the number to which you must raise a to get x."
and that therefore saying that log_a x = y is exactly the same thing
as saying that a^y = x.        
 
2. That logarithmic function  f(x) = log_a x  is the inverses of exponential functions with base a.    

3.  The properties of the graphs of logarithmic functions with
various bases, how they compare to each other, and how they
are related to the graphs of the exponential function with 
the same base. 

4.  The convention that  ln(x) = log_e x ("natural logs") and log(x)=log_10 x  ("common logs").  

You should be ABLE TO

1.  Convert exponential equations to their logarithmic equivalents
and vice versa. 

2.  Find inverses of log and exponential functions. 

3.  Solve simple exponential and logarithmic equations. 

4. Solve a variety of problems about exponential
growth and decay, including compound interest, 
population growth, radioactive decay. (This 
will be a continuing thread through the next few 
topics.)