Nice explanation and if I recall correctly an underpromotion was included as a daily puzzle not so long ago, under promoting to a Knight to solve it, very sneaky but it could mean the difference between a win or draw.
The value of underpromotion.
Sort:
“Grubby little beginner hands”? Aren’t you a beginner??
yes
nice puzzles, sadly I never end up with these kind of endgames. I always have more or less pieces rather than pawn endings 
Here is an evergreen example: white to play and win
#7
1...Rd6+
Hello everyone. A common sight I see on your grubby little beginner hands is when you get a pawn to the 8th rank on the end of the board, you snap it up and promote to a queen. In most cases, you would be right!
But in a few cases, the underpromotion is forced if you want to win!
Here's an example
In this puzzle, white is to move. To an untrained eye, you would think that black will be able to brute force through, force white's king out and promote to a queen. But, lo and behold...
Taa-daa! White has no legal moves and is not in check. White manages to get away with a draw by the skin of their teeth.
But, if you where black, how would you win this?
FUN FACT - The rarest move in chess is a Bishop Underpromotion.