A centrifuge is a device for applying force to a sample, usually by motor driven rotary motion of the sample. There are many different kinds of centrifuges, often for very specialized purposes.
The ultracentrifuge is a device invented in 1925 by Theodor Svedberg, which by use of very high G forces, and allowing the observation of sedimentation rates for macromolecules, allowed for the determination of their approximate molecular weights. Svedberg won the 1926 Nobel Prize in Chemistry for his invention.
Other, simpler centrifuges are used in biology and biochemistry for isolating and separating biocompounds on the basis of molecular weight. These will tend to rotate at a slower rate than an ultracentrifuge, and have larger rotors, and be optimized for holding large quantities of material at intermediate G forces.