No need to feel dumb! "Spawn" simply means that the reagent appears or reappears in a particular location. So the location that something spawns, means where it is programmed to appear. The rate that something spawns, means how quickly it will come back once harvested.
People also speak of enemies spawning. That means how quickly they reappear after being defeated.
"Spawning" is the in-game creation of an NPC or an item. A "spawn" spot is a certain place where an NPC or item (reagent) will appear.
For example, after you defeat an NPC, it will appear again after a few moments. Another example: you pick up some mist wood in a certain spot in Unicorn Way. Ten minutes later, it appears in the same spot again.
Spawning is just a term that decribes the item's return. Like when you pick up a mist wood, it disappears. Well, it will eventually come back for the next player to pick up (though usually in a different spot) and that is what is known as spawning.