Question

how does a traditional spade differ from round and square shovels?
has heavily curved sides
is much wider and longer
has a steel handle
is flatter and without curved sides

Explanation:

A traditional spade is characterized by its flat design without curved sides. Round shovels have curved sides for scooping, and square shovels may have more angular but not flat - without - curved - sides features. The handle material (steel) is not a defining difference as handles can vary for all types. Width and length can vary among different tools and are not the key differentiator here. Curved sides are more associated with round shovels.

Answer:

is flatter and without curved sides