Any Functional Difference: AR "Invoice" vs "Debit Memo"?

Can anyone provide any feedback RE whether or not there are any functional differences between an AR "Invoice" and an AR "Debit Memo"?

For all intense purposes - these appear to be "TX Types" - and possibly as a means to organize/track transactions in AR. Granted - you may also have seperate distributions assigned to each. But, beyond that, is there any deviations between these two "TX Types" by which Lawson AR will treat them differently from a functionality/data perspective?

Any feedback would be most appreciated.