A 500 internal server error is a generic 'something went wrong on the server' message. Unlike a 404 (page not found), a 500 means the page exists but the server hit a problem trying to build it.
Also known as: Server error, HTTP 500
In plain English
A 404 says "that page isn't here." A 500 says "something broke while I was trying to give it to you." The page and its address are fine - the server choked while assembling the response, usually because of a PHP error, a plugin conflict, or a resource limit.
Why it matters for your business
Unlike a 404, a 500 usually means something is genuinely broken - and if it's happening site-wide, your whole website may be down for every visitor. It's one of the most common reasons sites go offline unexpectedly.
When you'll run into it
After a plugin or theme update, when PHP memory runs out, or when two pieces of software on the site disagree with each other.
Run into this on your site?
WordPress Hosting