"Instances" versus "Linked Duplicates"

chunck In the video you're creating "Linked Copies" of the "Hat Mesh Object" and the "Lattice". So you're creating two new object, one of which containing new mesh data. Manipulating one object also changes the other object, but they're nevertheless separate objects that are just connecting in terms of editing. 

An "Instance" of a "Mesh Object" on the other hand doesn't create new geometry but adds an empty at the cursor location and an "3D Image" of your original object with an offset to the empty that reflects the distance between the orignal object and the "Wordl Origin":

1) Put the "Hat Mesh Object" and the "Lattice" into a new "Collection" and name it "Hat"

2) Snap the "Cursor" to the position of the "Hat Mesh Object" and move the latter with its "Lattice" to another location

3) Add a new "Hat Collection Instance"

4) You'll get an "Empty" and an "Image" of the "Hat Collection" with an Offset mentioned above

5) Parent the "Lattice" to the "Hat Mesh Object"

6) Clear the location for the "Hat Mesh Object"

The "Instance" of the "Hat Mesh Object" is now at the "Instance Empty" which is at the original position of the "Hat Mesh Object"

7) New "Instances" of the "Hat Mesh Object" can be added to the scene and transformed be manipulating the "Instance Empty" accordingly

Now for one "Hat" in the scene it's actually easier to create a "Linked Copy" of the "Hat Mesh Object" and its lattice. But for a bigger amount of copies, "Instances" save a lot of geometry and therefore memory space.