Hi!!
They already explained very good above, but I've got something to add:
Imagine a two dimensional being imagining a cube... he might think of two squares, one inside each other joined by the edges... that's a vague idea of a cube :D.
What you think of a hypercube is really the 2D visualization of the 3D cross-section of a 4D object... but that's hard to do with a glome (hypersphere).
Imagine you show a sphere to a two dimensional being... he would just see a dot that increases to a big circle and then decreases again to a dot to dissapear. That's the succesive show of 2D cross-sections of a sphere. The sphere is intersected by the his plane (his 2D world is a plane).
The same happens for us. Any visualization you can do of a glome is really a sphere, of smaller or bigger size depending which cell, volume or 3D space is crossing ours (our space). That is, we can only see the parts of the glome intersecting our space. But like a sphere is volume inside a curved plane, a glome is hyper-volume (a part of tetraspace, hyperspace or 4-space) enclosed by a curved space, which can be only PARTIALLY intersected by our 3D space. It isn't hard, but instead impossible to imagine different spaces existing.
You can possibly imagine two parallel lines, two crossing planes, a curved line, ... but you simply can't imagine two paralell spaces, or two spaces intersecting in a plane... you haven't that power. Neither do I.
Well, bye hope it helped ^.^ !!
Edit:
To the person below:
To represent a hypersphere as you represent a sphere, you would need a 3D volume or a cube of paper or whatever xD.
For the sphere, you draw a circle, that is, 3D to 2D.
For the glome you should draw a sphere, that would be, 4D to 3D.
The same happens with Circle-Ellipse to Sphere-Ellipsoid (again crossing dimensions).
Now, if you could see that 3D object we just created in space, and put it into a paper, would look exactly like a sphere ;). Glome = Sphere in a paper.
To see what fails in our glome, see firsts what fails in the sphere... The sphere is draw on just 1 plane, no depth for it :(... same for glome, it is drawn in just 1 space... no 4D orthogonal extra direction for it :(...
If the diameter of the glome was marked, when it crosed our spaces we would see that sphere within ours, going smaller as the bigger sphere does :P.
Hard to imagine :D...