Update documentation/docs/14-configuration.md

Co-authored-by: Ben McCann <322311+benmccann@users.noreply.github.com>

documentation/docs/14-configuration.md

@@ -164,7 +164,7 @@ An object containing zero or more of the following `string` values:
 
 See [Prerendering](#ssr-and-javascript-prerender). An object containing zero or more of the following:
 
-- `concurrency` — how many pages can be prerendered simultaneously. In cases where prerendering performance is network-bound (for example loading content from a remote CMS) this can speed things up
+- `concurrency` — how many pages can be prerendered simultaneously. JS is single-threaded, but in cases where prerendering performance is network-bound (for example loading content from a remote CMS) this can speed things up by processing other tasks while waiting on the network response
 - `crawl` — determines whether SvelteKit should find pages to prerender by following links from the seed page(s)
 - `enabled` — set to `false` to disable prerendering altogether
 - `entries` — an array of pages to prerender, or start crawling from (if `crawl: true`). The `*` string includes all non-dynamic routes (i.e. pages with no `[parameters]` )