How does the underscore forward movement work? _f

Question

I was recently watching a more advanced vim tutorial on youtube. One of the commands used was _f. This was actually just part of a longer macro being demonstrated and the underscore wasn't commented on.

Using the letter e as an example: I tried it on a long line of text and there is indeed a difference between fe and _fe but I can't understand what is happening. _fe doesn't go to the first, second, or last occurrence of e on the line.

What is _f doing? Bonus points for why is it doing it!

EDIT to add example

The following is a single line of random text. With my curser at the beginning of the line fe arrives at the first e, which I have highlighted and demarcated.

2:5 Now no shrub of th**e** field had yet grown on the earth, and no plant of the field had yet sprouted, for the Lord God had not caused it to rain on the earth, and there was no man to cultivate the ground. 2:6 Springs would well up from the earth and water the whole surface of the ground. 2:7 The Lord God formed the man from the soil of the ground and breathed into his nostrils the breath of life, and the man became a living being.

However if I use _fe it skips over the first two instances of e and lands in the third instance.

2:5 Now no shrub of the field had y**e**t grown on the earth, and no plant of the field had yet sprouted, for the Lord God had not caused ...

I have tried it with other letters, with the similar result of not hitting the first occurrence of that letter.

Answer 1

_fe should go to the first occurrence of e on that line. Can you give an example of where it doesn't?

From :h _:

_  <underscore>         [count] - 1 lines downward, on the first non-blank
                        character linewise.

In other words, _ without a count moves to the first non-blank character of the current line, then fe goes to the first instance of e.