How browser cache works
When someone opens a page, the browser does not download one file. It downloads the HTML, then the stylesheet, the fonts, the logo, the images and any scripts the page depends on. Most of those files are identical on every page and on every visit, so the browser saves a copy on the device rather than asking your server for them again.
Your server controls that behaviour by sending instructions alongside each file. A Cache-Control header sets how long the copy may be treated as fresh. A validator such as an ETag gives the browser a fingerprint it can send back later to ask a shorter question — has this changed? — which the server answers without resending the file. Nothing in this is a setting inside WordPress; it is decided by the server, the host or a caching plugin that writes those headers for you.
Why browser cache matters
It changes the second visit far more than the first. A visitor arriving cold must fetch everything, so the first page view is as slow as the connection allows. Once assets are stored, every page after that loads mostly from the device, and the site starts to feel like an app rather than a series of downloads.
That gap matters most where connections are mobile and metered, which describes a large share of traffic in Nepal. Reusing stored files means fewer requests, less data spent by the visitor, and less load on your hosting. It also takes pressure off the parts of page speed you cannot control, because a file that is never requested cannot be slow.
Common mistakes with browser cache
The most damaging mistake is a long cache lifetime on a file whose name never changes. Edit the stylesheet and returning visitors keep the old one until their stored copy expires, so a design fix looks perfect to you and broken to everyone who has been to the site before. The cure is a fingerprint in the filename or query string, so a changed file is simply a different file.
The opposite error is telling browsers not to store anything, usually left behind after a debugging session. And almost everyone at some point tests their own site in a browser that already holds every asset, decides it is fast, and never sees what a first-time visitor experiences.
How to act on it
Give static assets — images, fonts, compiled CSS and JavaScript — a long lifetime and change their filenames whenever their contents change. Give HTML a short one, or none, because that is the file that must always be current. After any release, clear the caching layers you control and check the page in a private window with caching disabled in developer tools.
Do not expect this to fix a slow server. Browser cache removes repeat requests; it does nothing about the wait before the first byte arrives. If the cold load is the problem, the work sits in hosting and page speed optimisation instead.