"Guard the sense doors"- What does this mean, and what is it's application? What does it mean to "guard the sense doors"? What is the practical application of this concept in daily life? For example, does this concept mean that a heterosexual male should entirely avoid looking at women?

Thank you
Yuttadhammo Bhikkhu answers a question about "guarding the senses" in this video (at time 34:40).

Guarding the sense doors is a way of protecting ourselves from being overcome by passion for the sensed object (which leads to dukkha). In his video Yuttadhammo mentions three ways to do this.


Physically avoiding the object (in relation to your example, when on alms round monks may keep their eyes facing down to avoid lust from seeing a beautiful woman).
By developing samadhi the mind is disconnected from the sense doors (only the sixth sense "thought" is present)
By developing insight we know the inherent dukkha of sensed objects, therefore no passion arises for them when they are sensed.


The third approach is part of the goal, the first two are training practices to help us maintain a calm mind to achieve the goal.