An email extractor and an email finder both end with addresses in hand, but they work in opposite directions. An extractor pulls addresses that already appear in text, files, or HTML you provide. A finder starts from a person or company and tries to discover or predict an address that isn't written down anywhere.
The difference is discovery versus extraction. Extraction is deterministic - the addresses are already there. Finding is probabilistic - it guesses patterns like first.last@company.com and verifies them. Each fits a different stage of list building.
