The graph is rather difficult to interpret simply. For a rather full explication of what it means, see Review of the Universe: Power Spectrum.

But rather vaguely???, it shows of frequency of pairs hot and cold spots of various angular separations (as indicated by the upper axis) on the sky in the cosmic microwave background (CMB) (CMB mean temperature T = 2.72548(57) K (Fixsen 2009) (FK-652--653). The large/small angular separations are on the left/right.

The data points come from various experiments: WMAP (2001--2010), ACBAR (2000-2008), BOOMERanG (1997--2003), CBI (1999--2008), and VSA (2000---2008).

The curve is fit to the data---but with how many free parameters???---of what is called a scale-invariant power which is a prediction of standard inflation models of the inflation paradigm irregardless of the details of the inflation mechanism (CL-263,265,274--275; Gr-309).

The fact that the inflation paradigm predicted the observations is an astonishing triumph of the inflation paradigm.

The successful prediction does NOT prove the inflation paradigm, but it certainly strongly supports it.

Credit/Permission: NASA, WMAP Science Team, 2006 (uploaded to Wikimedia Commons by User:Pieter_Kuiper, 2007) / Public domain.
Image link: Wikimedia Commons: File:PowerSpectrumExt.svg.
Local file: local link: cmb_power_spectrum.html.
File: Cosmology file: cmb_power_spectrum.html.