I always think of using juice concentrate to understand espresso better. the juice you have go dilute before drinking it.
Say if you start off with 30g of juice, (this represents your dry dose) and then add 30g of water (your yield), your drink will be really strong, and as you keep adding water it will get weaker and weaker.
Increasing the yield will make the espresso more delicate, sweeter and complex; to a point, after that point it becomes acrid, weak and bitter. if you type in sweetspot extraction in coffee into google it will come up with Pergers blog post, which is more informative than me!