I learned about this item rather late in life: shovels and spades and snow shovels I learned about quickly, but this one escaped my notice. It turns out to be very useful when you need to break up the soil, especially when your better half plants bulbs--a shovel's wide slice dissects more of them than the few spikes of the garden fork.
A shovel also tends to bring dirt up more as clods, and so requires a little more work to break it up so you can stir in the fertilizer or whatever. A fork is also handy when you're trying to trace grass/mint/bindweed roots traveling sideways--you can figure out which way they're going and pull more of the root out.
However
A word to the wise: the garden forks we have (garage sale specials) don't have tops as flat as a shovel's (or even the example above) for planting your foot on to ram it into hard or rooty soil. Look for flat tops when you get one.
If you try to push the more rounded models with your foot, you'll force your muscles and tendons to work harder to try to hold your foot straight and not turn sideways. You may not notice your mistake until the next day, but you'll notice. It's been a week, and whatever the tendon is attached to the tibia medial malleolus is still sore to the touch.
