It's brought up by the Talmud because it's very practical there. It's really something a person has to be careful about throughout the course of the day, literally, when it comes to tefillah (prayer), berachot (blessings), or learning Torah. What is this halacha (Jewish law)? A person must make sure not to touch any area on my body that is normally covered. And that area is included from my arms up until my elbow. It comes to my legs all the way down. Anywhere over here that's covered, I have to avoid touching. If I touch that, then the rule is: if I have access to a sink, I have to wash my hands. Otherwise, there are different things you can wipe with that will also do the trick. But this is the halacha in general.
Before you make berachot, before you pray tefillah, before you learn Torah, you have to avoid touching these things. This also includes scratching one's head, an area that should be covered or is normally covered. When scratching our heads, it's a halacha for a person to make sure to wipe their hands or, better, wash their hands before doing these things, like tefillah, Torah, and berachot. That's the halacha in general. Specifically, this comes up because very often we just change. If we change, we might have touched something. Therefore, that's a halacha that applies. Similarly, it applies to touching your shoes as well. Where is there a bit of debate? The debate applies when it comes to touching your socks. Whether that requires the same law or not, we'll discuss tomorrow. Have a great day, Kabbalah.