You don’t have to use Cloudflare, but since it’s the most popular and free solution I’m specifically going to talk about Cloudflare.
What happens when you get tons of people coming to your website? Does your website stay up, or does it basically shut down because your site can’t handle all the people. What if there is a free solution to help lessen the chance of your website shutting down?
This is where Cloudflare comes into play, it acts between your potential customer and your website. Cloudflare puts your website content on their servers (don’t worry you can still update your website like you normally do, and you can delete everything Cloudflare has if you want) so it ensures that your content is quickly available around the world. As well, it helps to protect against unwanted attacks against your site (the free plan does some basis and the more you pay the more protection you get).
Using Cloudflare (or another free / cheap cdn) is really the only cheap / free way to ensure your site says up when tons of people visit your website.
Wondering how to install Cloudflare on your WordPress website? Read this great article by createandcode.