Direct Answer
On-page SEO is everything you control on your own website: titles, headings, schema, internal links, content quality, and page speed. Off-page SEO is everything that happens elsewhere: backlinks, citations, brand mentions, and reviews. Both matter; on-page is usually the higher-ROI starting point because you fully control it.
Voice answer (≤30 words)
“On-page SEO is what you control on your site. Off-page SEO is backlinks, citations, and mentions from other sites.”
Fix on-page first. There is no point in earning backlinks to a slow, poorly-structured page.
Off-page SEO compounds slower and is harder to measure but is the moat that keeps competitors from passing you once you rank.
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