In one sentence: Browser caching is a website telling a visitor's browser how long it may keep its own copy of files like the logo, stylesheet, and fonts, so that later pages and later visits load those files from the device instead of downloading them again.
The first time someone opens your site, their browser has to fetch every piece: the HTML, the stylesheet, the fonts, the logo, the photos. Along with each file, your server can attach a note saying how long the browser is allowed to reuse it.
From then on the browser checks its own storage first. If the copy is still inside its allowed window, it uses that copy and skips the trip to your server entirely. If the window has passed, it asks whether anything changed, and often the answer is no.
A contractor's version of the same idea: you keep the common tools in the truck instead of driving back to the shop for each one. Nothing about the job changes. You just stop making the trip.
The catch is the mirror image of the benefit. Tell browsers to hold a file for a year and they will, including the copy of the file you just changed. The durable answer is not a shorter window. It is to publish the changed file under a new name, so the browser meets a file it has never seen and goes and gets it.
Picture how people actually shop for a local service. They open your homepage, tap through to the service they need, then check the contact page to see whether you cover their town. That is three pages, and the logo, the fonts, and the stylesheet are the same on all three.
With caching in place, only the new words and images load after that first page. Without it, the same files come down again every time, and on a weak connection each one is another wait.
The same thing helps the visitor who found you last Tuesday, thought about it, and came back to call. Their device may still be holding most of your site.
Be clear about the limit, though. Caching does nothing for a first-time visitor, because they have nothing saved yet, and the first visit is usually the one that turns into a lead. It rewards the second page onward. It is not a substitute for a page that is light to begin with.
Cache rules live in server configuration rather than in your pages, so they tend to get set once and then go unexamined for years. That makes them a good standing item for website maintenance.
The browser cache is the one on the visitor's device. A CDN cache holds copies on servers placed near your visitors. Your host may run a page cache of its own on top of that. They are separate layers with separate rules, which is why a change can look live in one place and stale in another.
The risk worth naming is a stale page, not a stale logo. If you moved, or your hours changed, or the number on the site rings a phone you no longer carry, an aggressive cache means some people keep seeing the old version well after you fixed it. That is the reason cache lengths get set per file rather than in one blanket rule.
It is also why your developer sees the update and you do not. Their browser went and got the new file. Yours is still showing the one it saved.
Almost always because your browser is showing a file it saved earlier. A hard refresh, or opening the page in a private window, will show you the current version. If other people are seeing the old copy too, the changed file needs to be published under a new name.
They cover different halves of the problem. Browser caching helps a person who has already been to your site. A CDN helps the first visit, by serving your files from a machine closer to where that visitor is standing. Most sites end up using both.
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