Mechitzos separating men and women - when and why?

Kolel L'horaah Ma'asis Crown Heights - Shiur 1 on halachic topics - by Rabbi Shraga Dovid Homnick, Sgan Rosh Kolel, tracing the sources mandating a mechitzah for tznius in shul, at shiurim, weddings and events, and the type of mechitzah necessary

https://www.youtube.com/watch?v=g1onAGXf8wk