a diffractogram
A diffractogram is simply the graph the diffractometer draws for you: measured X-ray intensity (counts) running up the vertical axis, plotted against the scattering angle 2-theta running along the horizontal axis. What you see is a landscape — a row of peaks rising out of a gently rolling background. Reading a diffractogram is a lot like reading a barcode: the pattern of lines, not any single line, tells you what the material is.
The skill is knowing that a diffractogram carries three separate readings, and not muddling them. The peak positions (where along 2-theta each peak sits) convert by Bragg's law into d-spacings, which give the size and shape of the unit cell. The peak intensities (how tall each peak is) encode the motif — which atoms sit where inside that cell. And the peak widths (how sharp or broad each peak is) report on the microstructure — crystallite size and internal strain. Underneath sits a smooth background from air scatter, sample fluorescence, and any amorphous (glassy) content.
Because one quick scan bundles geometry, motif, and microstructure together, the diffractogram is the central object of practical X-ray work. Stay honest about what it is, though: it is a one-dimensional projection of a three-dimensional reality, so peaks routinely overlap and a beautiful, clean-looking pattern can still fail to pin down a structure uniquely without a model to fit against.
Reading a quartz diffractogram: the tall peak at 2-theta = 26.6 degrees (position) gives d = 3.34 angstrom for the (101) planes; its height (intensity) marks it as the strongest reflection; its narrowness (width) says the crystallites are large and well-ordered.
One scan, three independent readings — position, intensity, width — each a different piece of the story.
Do not read a peak's height as its position or its width as its intensity — the three readings answer three different questions (unit cell, motif, microstructure).