A sitemap is a file, usually sitemap.xml, listing all the pages on your website. Search engines use it as a table of contents to discover more quickly which pages exist and when they changed. It does not guarantee a good position, but it helps in particular with larger sites and with new pages. You submit it through Google Search Console; on a well-built site it updates automatically.
A sitemap is a table of contents for your website, written in a format search engines understand. Usually it is a file at yoursite.nl/sitemap.xml. It lists which pages exist and when they were last modified.
A sitemap helps Google find your pages. It says nothing about how good they are. A page that appears in the sitemap but that nothing links to and nobody cares about will not rank because of it.
The greatest benefit is with new pages and with large sites. If you have five pages all reachable from the menu, Google will find them without a sitemap. If you have two hundred, some buried deep, a sitemap genuinely helps.
On the sites we build the sitemap is regenerated on every change, including the language variants. See also our explanation of SEO and AEO.
For a site of five to ten pages all reachable from the menu, Google will find everything without a sitemap. It does no harm and costs nothing, so we include one as standard. As soon as a site grows to dozens of pages, or when there are pages not directly in the menu, a sitemap becomes genuinely useful. It helps most with new pages: those are typically picked up faster when listed in the sitemap than when Google has to discover them through links.
No, and that is a persistent misconception. A sitemap helps Google find your pages, but says nothing about their quality or relevance. Your position is determined by content, structure, speed and the links pointing at your page. A sitemap at most speeds up the moment a new page gets picked up. Anyone promising that submitting a sitemap improves your rankings is selling you something that does not exist. Invest that attention in pages that answer a real search question instead.
On every change to your site structure: new pages, removed pages or changed addresses. In practice that means automatically. A hand-maintained sitemap is outdated within a month, and an outdated sitemap costs more than it delivers, because Google keeps encountering addresses that no longer exist. On the sites we build the sitemap is regenerated on every publish, including the last-modified date per page and the link between language versions.