Directory traversal is when an attacker uses the software on a web server to access data in a directory other than the server's root directory. If the attempt is successful, the threat actor can view restricted files or execute commands on the server.
Command injection is an attack that involves executing commands on a host. Typically, the threat actor injects the commands by exploiting an application vulnerability, such as insufficient input validation.
The attacker is attempting to traverse the directory of the host and execute the cat command which could be used to print the contents of a file.