IA 32 architecture segmentation
In the good old days of the 80286, the address space had 24 bits (16 MB), but registers still had 16 bits (64 KB). So you had a 16-bit selector, pointing to a segment descriptor containing the 24-bit base address of the segment, and a 16-bit offset into the segment. You needed multiple segment to access the entire address space.

With the 32-bit 80386, both the address space and the register size were enlarged to 32 bits. So now you have a 16-bit selector, pointing to a segment descriptor containing the 32-bit base address of the segment, and a 32-bit offset into the segment.

This means that IA-32 allows a single segment to cover the entire address space. And this is in fact how most operating systems work nowadays: they use a fixed segment with a base address of zero, and otherwise ignore segmentation.