I'm new to Tor. What is Application Boundaries Enforcer (ABE) and ClearClick and why should I have them turned on or off?
ABE and ClearClick are part of the NoScript add-on.
ClearClick automatically detects clickjacking attempts, and shows you a warning. For exact details, read the FAQ here: https://noscript.net/faq#qa7_4
ABE is the Application Boundaries enforcer, and protects against cross-site request forgery, or CSRF. It basically blocks websites from accessing resources on your local network. More detailed information is available on Wikipedia: https://en.wikipedia.org/wiki/CSRF
Both of these features help keep you safer, so it's probably best to keep them turned on.