The `min` and `max` values provide an outer bounding box for all `POSITION` data within a given accessor.  Accessors typically contain multiple vertices, for example all of the vertices of a particular primitive, and then `min: [x, y, z]` and `max: [x, y, z]` will offer the bounding box for that primitive.

For your second question, let's look at the mesh structure from [BoxTextured.gltf](https://github.com/KhronosGroup/glTF-Sample-Models/blob/0bc74b12b2de22a1267ccab819efcf8c6a4f3dc8/2.0/BoxTextured/glTF/BoxTextured.gltf#L44-L56):

    "meshes": [
        {
            "primitives": [
                {
                    "attributes": {
                        "NORMAL": 1,
                        "POSITION": 2,
                        "TEXCOORD_0": 3
                    },
                    "indices": 0,
                    "mode": 4,
                    "material": 0
                }
            ],
            "name": "Mesh"
        }
    ],

In the above example, `mode: 4` is an enum, where `4` means `TRIANGLES`.  The `indices` are stored in accessor `0`, and the `POSITION` data is stored in accessor `2`.  So, accessor `2` will contain a list of vertex positions, but each vertex is allowed to be referenced by multiple triangles.  The indices in accessor `0` declare the triangles by indexing into the list of vertices.

Here's a sample of the start of accessor `0` from this model:

    0 
    1 
    2 

    3 
    2 
    1 

    4 
    5 
    6 

    7 
    6 
    5 
    ...

And this is a sample of the contents from the start of accessor `2` in this model:

    -0.50000    -0.50000     0.50000 
     0.50000    -0.50000     0.50000 
    -0.50000     0.50000     0.50000 
     0.50000     0.50000     0.50000 
     0.50000     0.50000     0.50000 
     0.50000    -0.50000     0.50000 
     0.50000     0.50000    -0.50000 
     0.50000    -0.50000    -0.50000 
     ...

In this manner, the sample model builds a cube by winding triangles around vertices at the corners.

For a more graphical explanation of this, check out the [glTF Overview Card](https://raw.githubusercontent.com/KhronosGroup/glTF/main/specification/2.0/figures/gltfOverview-2.0.0b.png) - same image is found [here][1].


  [1]: https://github.com/KhronosGroup/glTF#overview