Caching is the saving of specific elements on your website so they do not need to be "re-built". This can be very effective in speeding up your website as these elements do not need to be regenerated.
While you are building your website, it's important to consider how it navigates and looks, but also how it performs in terms of speed. While you can always remove items from your webpage and be cognizant of what items to load on the page, there are a few techniques that can help your webpage still have all of the items needed on it and still run fast.
Today there are many different options that you hear about to help make your website faster and more appealing to humans. No one likes a slow website, but how fast is too fast? Is there a limit or should you just keep enabling everything that you can to make your website load in the shortest amount of time possible?