That’s where it gets complicated. We don’t know because we can only observe 13.7 billion light years in every direction. So what we see is a sphere with us at the center. But there are some other things that suggest that the universe is a hypersphere or a hypertoroid.

It’s not possible for us to picture these objects except by approximation, or with math, or with analogies. But a short explanation: A sphere is a circle extended into an additional dimension. You can visualize that. A hypersphere is a sphere extended into an additional dimension. Can’t visualize it, but that’s what it means.

A torus is a donut shape, so a hypertoroid is a donut extended into an additional dimension.

There are videos about hypercubes, and hyperspheres, which attempt to help picture what it’s like, but because our minds operate in 3 dimensions, it’s not capable of truly comprehending these 4 dimensional objects.