This question is fairly straight forward, but I can't it figure out.
I am using the schema browser in the IDE to query some records and the SystemModstamp is actually 1 second later than the LastModifiedDate so they are obviously different. But hence the question: what is the difference?
LastModifiedDate is the date the record was last updated by a user. SystemModstamp is the date the record was last modified (by a user, workflow, trigger, etc.).
If you ask nicely, salesforce will let you set the last modified by (as in, you're importing records after a merger and want to maintain the created and modified stamps from the old system).
You can't ever touch the system modstamp.
SystemModStampdoesn't seem to capture if the record is updated via apex trigger nor via formula field.