WordPress authors have the option to create pages and posts in a Visual Editor or a Text Editor. While the Visual Editor does a reasonably good job with its toolbar options and easy editing environment, the use of the Text Editor allows maximum flexibility on how to organize content.
See more on https://teslathemes.com/blog/beginners-guide-to-using-the-wordpress-html-text-editor/
For inserting codes like PHP codes, you need to either add a PHP code plugin or modify the function.php file in your active theme. See more on http://www.emanueleferonato.com/2011/04/11/executing-php-inside-a-wordpress-widget-without-any-plugin/
However, if your website is a relatively simple one and doesn’t need complex features. Then you can use this way to code your pages.
EsyWebsite can help you to better build the page by using dedicated plugin-like or custom-written php codes to create the page. With us, the cost of using both ways is about the same. By using us, you will be ensured that your website can be better future-proof.