With an aperture of 3.5 meters, Herschel is the largest space telescope yet flown (Hubble is 2.4 meters). Perhaps more importantly, Herschel works in the far-infrared part of the spectrum: a poorly explored realm between the familiar, shorter-wavelength "warm infrared" and the millimeter-wave and microwave radio bands. Its cameras can work at six far-infrared and submillimeter colors, with wavelengths around 70, 110, 160, 250, 350, and 500 microns. Such wavelengths are the ones most strongly emitted by objects that are extremely cold — not far above absolute zero.
What we see in the picture here (a mosaic of many small frames) is mostly very cold interstellar dust. It's not reflecting starlight but glowing with the characteristic, very weak thermal emission for such temperatures. Blue and green here represent two of Herschel's shorter wavelengths, highlighting less-cold dust. Red indicates longer wavelengths and colder material. Notice the bright points of star formation happening inside a few of the densest, coldest filaments, almost like pearls on a string.
This is just a taste. In the coming months and years there'll be lots more.