Leading, Horizontal Scale, and Vertical Scale

Leading- Leading in photoshop is when you have one size of font, and its the next font higher or lower. For example, say you're at font 72, the next leading font is 73.

Horizontal Scale- Horizontal scale is when you practically stretch your font horizontally making the lettering of the original font short and long. An example is shown below as letter C.

Vertical Scale- Vertical Scale has the same concept as the horizontal scale except the vertical scale is stretching the font vertically making the lettering long and skinny. An example show above as letter B.