This means the legal agreement you accepted when you joined Snapchat can be changed in ways that are less favorable to you, and simply continuing to use the app constitutes your legal agreement to the new terms even if you did not explicitly review or accept them.
Snapchat's Terms grant the company a broad, royalty-free, worldwide license to use, reproduce, modify, and distribute anything you post — including photos, videos, and messages — which persists even after you delete content in some contexts. US users waive their right to participate in class action lawsuits and must resolve disputes through binding individual arbitration, which significantly limits legal recourse. You can review and adjust your privacy and data settings within the Snapchat app under Settings > Privacy Controls to limit some forms of data use.