radiation, alpha: This radiation consists of two protons and two neutrons. (This is the same as the nucleus of a hydrogen atom.) Alpha particles travel about 7% of the speed of light (2.2*10^7 m/s) and require very mild shielding as protection against them --- a few sheets of paper. Although they are easy to protect against externally, this radiation causes the most damage if it can reach beneath the skin. If one ingests or breathes alpha-radioactive dust (which isn't common) it can do some damage.
radiation, beta: This radiation consists of electrons or positrons. Beta particles travel anywhere from a quarter of to nearly the value of (99%) the speed of light and require mild shielding as protection against them --- 15 meter of air or a millimeter or so of aluminum.
radiation, gamma: This radiation consists of photons (light). It is high-energy radiation in the gamma frequency. Since it is high energy, thick shielding (several feet of concrete or several centimeters of lead) is necessary as protection against it.
rotate: To rotate is to turn about a point which is (usually) held fixed. (It is possible to rotate about a translating point.) There are two contexts for this: First, an object can rotate either about another object (orbit) or about an axis through that object (spin). Second, if one rotates a coordinate system, then the origin of that coordinate system is held fixed and the axes (plural of axis - see dimension and coordinate system) are rotated around the origin.