URLs are assets: they accumulate links, bookmarks and rankings over years. A 301 says 'that asset moved, permanently — same thing, new address' and transfers the accumulated value. A 302 says 'temporarily elsewhere' and keeps the value parked at the old URL, which is why picking the wrong code quietly leaks authority.
The discipline is mapping: every retired URL gets a 301 to its closest living equivalent, not a blanket redirect to the homepage — a redirect to somewhere irrelevant is treated as a soft 404. Chains (A→B→C) get flattened, and the sitemap lists the new URLs, so search engines stop walking the old path.
Related terms
Canonical URL
A tag naming the one 'real' address for content reachable at several URLs — so search engines rank the copy you meant, once.
Indexing
A search engine adding a page to its searchable database — crawling fetches it, indexing makes it findable; unindexed is invisible.
SEO
Search engine optimization — making pages findable, indexable and worth ranking: technical health plus content people actually want.
The bench this belongs to
Web performanceA rebuild that loads on a phone on mobile data, in the country your customers are actually in. Core Web Vitals are the measurement, revenue is the point.
