What a redirect is and the difference between 301 and 302
In short
A redirect is an automatic forward: a person or search engine visits one address but lands on another. You need it when a page changes address or you merge several versions into one.
301 versus 302
A 301 is permanent: "this page has moved for good." It passes almost all the built-up link weight and rankings to the new address. A 302 is temporary: "back soon," and passes no weight. Mixing them up is a common, costly mistake - a 302 on a permanent move quietly loses your rankings.
When a redirect hurts
Chains, where A goes to B, B to C, C to D: each hop slows loading and wastes crawl budget. Loops, where a page redirects to itself in a circle. A redirect to a 404 page. All of these are better straightened into one direct hop.
Common mistakes
A 302 (temporary) instead of a 301 for a permanent move - no weight passed
Redirect chains several hops long instead of one direct jump
A redirect leading to a missing page or looping endlessly
Check how this looks on your site
A free 30-second audit shows whether everything is fine on your site.
Use 301 when a page moved for good: new address, merged duplicates, switch to https. Use 302 when it is temporary: a promo, maintenance, an A/B test. When in doubt, it is almost always a 301.
How do I check redirects?
The free SEO Nerve audit traces the redirect chain and warns about temporary 302s, long chains, loops and redirects to errors.