What It Is
Normally, a WordPress server builds each page on demand, running code and pulling content from the database every time someone visits. A server cache saves the finished page after it is built and hands that saved copy to the next visitors. It is like a coffee shop brewing a big pot of the house blend in advance, instead of grinding fresh beans for every cup.
Why It Matters for Your Business
Caching can make a site dramatically faster and lets the same server handle many more visitors. That matters during busy moments, like a restaurant posting a new menu or a shop running a sale. Faster pages also help search rankings and keep impatient mobile visitors from leaving. Server caching is often built into managed WordPress hosting.
Good to Know
Some pages should never be cached, such as shopping carts, checkout and account pages, because each visitor needs to see their own information. Good caching setups exclude them automatically, but plugin conflicts can cause problems. If you update a page and still see the old version, clear the cache. Running several caching plugins at once often makes things worse, not better.