Social media has its own vocabulary, and much of it means slightly different things on each network. Reach and impressions are not the same number. Engagement rate changes depending on whether you divide by followers or by reach. Instagram now caps hashtags at 5, Threads counts emoji by their bytes and Bluesky counts graphemes. Then there is the developer side, from webhooks and rate limits to idempotency keys and MCP servers, which matters as soon as you automate posting or let an AI agent help.
This glossary explains more than 110 of those terms in plain language. Each definition is our own wording, kept to one to three sentences. Where a definition gives a number or a platform rule, it cites the platform's own documentation or a dated news report, so you can check it yourself. We review the list regularly and show the date it was last verified at the top of the page.
Use the search box to find a term, or filter by category:
- Metrics: what analytics numbers mean and how to compare them.
- Content: the parts of a post, from captions and hashtags to aspect ratios and link previews.
- Ads: the paid side, from CPM and ROAS to retargeting.
- Platforms: how each network works and what its features are called.
- Developer: APIs, tokens, webhooks and the protocols behind automation and AI agents.
- Strategy: planning, scheduling, approvals and working with creators.
Many entries link to a free tool that does the job for you, such as the engagement rate calculator, the UTM builder or the character counter, and to a /learn guide that goes deeper. Every term has its own anchor, so you can link straight to a definition, for example #engagement-rate.
The glossary is also available as JSON from the free PostBoost API and as the get-glossary tool on our MCP server, so your scripts and AI assistants can look up a term the same way.
Tracking what people say online about your brand, competitors and topics, including posts that do not tag you, to find trends, questions and problems.
See also: Mentions Share of voice