I see how some people just get the math, but I don't see why programmers here say they find it difficult to understand the window / offset explanation the article gives.

A "window" is a common programming term for a range between two values.

An "offset" is a common term for where a value falls after a starting point.

In simpler decimal and equidistant terms, the idea is to split a range of values in windows, divide each window in N values, and store an FP number by storing which window and which index inside the window (0 to N) it falls.

The FP scheme actually uses powers of 2 instead of equal distant windows (so the granularity becomes coarser as the numbers become bigger) but the principle is the same.