In the last decade the applications of the laser in surgery and medicine have increased dramatically. With the increase of indications has come a concomitant increase in possible classification of laser reactions, including the erroneous ‘low power laser ’, ‘high power laser’ and others. The author presents a classification which is based on the laser/tissue reaction rather than on the hardware used to produce the laser beam. Laser/tissue reactions fall into two broad groups. When the tissue reaction to absorption of the incident laser energy results in photodestruction of, or an irreversible photomodulated change to the tissue architecture, then the level of reaction is higher than the survival threshold of the target cells. The author refers to this as high reactive-level laser treatment (HLLT), or more generally as laser surgery. On the other hand, the level of tissue reactivity to very low incident power and energy densities is well below the cells’ survival threshold so that instead of being damaged the cells are directly activated by the low incident photon density. In this case the changes in the irradiated tissue are photoactive and reversible: the author refers to this group of reactions as low reactive-level laser therapy (LLLT), or more generally as laser therapy. In general when laser energy is incident on tissue, whether it is intended for laser surgery or laser therapy, it propagates into the target tissue in a wavelength-specific manner, but the resultant pattern, for example a HeNe laser viewed in a block of methylacrylate or an infrared laser viewed in vivo with a CCD camera, resembles very closely the shape of an apple. The author has used this basic apple shape and has modified it so that the ‘Laser Apple’ is capable of giving a range of information about the laser and its tissue effect, including the laser type, wavelength, output power, irradiated area, irradiation time and penetration depth: from these parameters the incident power and energy densities can be calculated. The apple itself can represent the scattering pattern and is capable of graphically demonstrating the range of tissue reactions which in turn give their name to the range of ‘Laser Apples’, such as the C-Apple (carbonization), V-Apple (vaporization) and A-Apple (activation).