Well I think these are just defined names.
Like variables you can define names and attach a certain value to it. So you can use the name and not the value in your code to make it better to read.
Example:
Code:

---

define _running, 2;
define _walking, 1;
define _jumping, 3;

define walk_mode,skill21;

action test_actor
{
  while(me)
  {
    if(my.walk_mode == _jumping) { //do this }
    if(my.walk_mode != _running) { //do that }
    //...
    wait(1);
  }
}

---

I guess you get the idea
If this is not the way the templates are working, just correct me
Haven't ever really worked with the templates.