Eon has a sphere, and now he wants more of them. There's an easy way and a smart way — and the difference is a lesson he's met before.
The manual way: Shift+D
To duplicate an object, you hold Shift + D and move the mouse — one copy appears. Great for one or two. But what if you wanted ten? You'd be pressing Shift+D over and over, by hand. Tedious!
The smart way: a modifier
A modifier changes an object without you redoing the work by hand.
The array modifier is the star here: tell it how many copies you want and how far apart, and the computer makes them all automatically, evenly spaced.
Wait — that's a loop!
This should ring a bell from the Coding Lab: if you're doing the same thing again and again, let the computer do it for you. The array modifier is exactly that idea in 3D — repetition, automated. Whether it's a loop in code or an array in Blender, the principle is the same: work smart, not hard.
Try it
You want a row of 8 identical fence posts. Place 8 by hand… or place one and tell an array modifier "make 8, evenly spaced." Which would you choose? (The modifier — and if you later want 12, you just change the number.)