Difference between open-ended and close-ended load testing tools

What is the difference between open-ended and close-ended load testing?
Thread-based load-testing tool comes in which category?
Which are some examples of load testing tools in each category?

Looks like you are speaking about closed vs. open workload models.

This classification based on closed/open systems separation:

• in case of closed system model a new request is only triggered by the completion of a previous request, following by a think time. System has negative feedback that makes it impossible to bury-out the service, so users wait for the responses before making new requests;
• in case of open system model new requests arrival independently of completions, e.g. according to a stochastic process or fixed trace. System has no negative feedback.

Based on this classification we can divide load-testing tools into following categories based on workload model used:

• thread-based model where each thread will wait for a response before sending another request - so request rate depends on response rate (load generator drives the load as fast as system can take it):
  • thread-based approach is VU [virtual user]-oriented while trying to simulate N users working together;
  • thread-based tools require a separate thread to simulate a user;
  • examples: JMeter;
• hit-based model
  • hit-based approach is RPS [request per second]-oriented while trying to produce N hits per second load;
  • hit-based tools use async approach and will always attempt to create defined request rate, queuing requests if necessary;
  • examples: tsung, Yandex.Tank.