what is the different between * and IP core multiplier

An example of switching to lpm_mult would be if you determine features of the DSP/embedded multiplier block are not being utilized when the multiplier is inferred when you were counting on it. Sometimes it is not possible for the synthesis engine to map all the features of the hardware multipliers so using lpm_mult gives you the ability to do this.

In the Quartus II handbook there is a chapter called something like "HDL coding guidelines". It probably does a better job explaining this under the section about multiplication.

I try to avoid using the LPMs whenever possible since I often create IP for different FPGA families and the hard block characteristics sometimes differ. So options of lpm_mult may vary between families which makes your implementation less portable as a result (you may not care about portability though).