In order to test the features of Burp Suite, we need to prepare our environment. There are many web applications that are vulnerable by design. These are created specifically for learning purposes, and they are great. As you master your skills in Burp Suite, I encourage you to look at various vulnerable web applications that are created and released. A good resource to find both online and offline versions of vulnerable web application software is OWASP.
OWASP maintains a Vulnerable Web Applications Directory Project, which can be found at https://www.owasp.org/index.php/OWASP_Vulnerable_Web_Applications_Directory_Project#tab=Main.