Call-to-action — an explicit instruction telling the viewer what to do next (follow, comment, click, subscribe, save).
A CTA closes the loop between content and outcome. Without one, even highly engaging content produces no measurable next-step behavior. Common short-form CTAs: "follow for more", "save this for later", "comment X for the link", "send this to a friend who needs it". Common long-form CTAs: "subscribe", "hit the bell", "link in description".
CTAs work better when they're single, specific, and aligned with the content's value. "Like, comment, subscribe, hit the bell, and share with three friends" is a non-CTA — it asks for everything, gets nothing. "Comment 'GUIDE' and I'll DM you the checklist" is a CTA — one action, one specific reward.
Placement matters. Short-form: CTA in the last 2–3 seconds or as the caption first line. Long-form: CTA at 30% (early), 70% (mid), and end. Newsletters: CTA in the P.S. line outperforms CTA in the body.