One of the primary tasks of professors is communication with their students. Communication typically involves lecturing, clarifying uncertainties, and receiving feedback. Lecturing happens at fixed times, but receiving feedback and clarifying uncertainties are continuous tasks. I am referring to clarifying uncertainties as continuous tasks because students can ask any doubt related to the course at any point before the final exam.
My question is related to clarifying uncertainties. This is an extremely important task. Although a professor resolves some of the student's uncertainties during lectures, students may have questions at any time, so professors need to be available.
In this context, I want to know the modern software followed by top university professors on uncertainty clarification.
Recently I came to know about Piazza, Slack, etc., in which a professor can solve questions of students at any time.
Are there other better websites or software, followed by top-edge professors, to clarify student uncertainty that ensure professors' availability online?