what does off page seo actually mean?

In practice: a properly filled-in Google Business Profile if you serve a local area, listings on the handful of directories that matter in your industry (not the hundred spammy ones), and being the source people quote - a survey, a stat, a straight answer on a niche topic. Journalists and bloggers link to whoever gave them the number.

Everything that happens away from your own site. Links from other sites are the big one, but it covers people mentioning your brand without linking, reviews, the profiles you hold on other platforms, how many people search for you by name. You control none of it directly, which is exactly why it carries weight. On your own pages you can simply assert that you're the best at something. Off page, somebody else has to say it.