An 8-K filing is a report that public companies must file with the SEC to announce major events that shareholders should know about. These "current reports" must be filed within four business days of the triggering event.

Common 8-K triggers include: earnings results, acquisitions and dispositions, executive officer changes, amendments to articles of incorporation, bankruptcy filings, and material agreements.

Note: 8-K filings disclose material events but the market impact varies. Always review the full filing on SEC EDGAR for complete details before making investment decisions.