Thrips species feed on a wide array of plants and other insects by first puncturing them with their mandibles (clearly visible in image), then drawing out the nutrients through a tube-like structure in the mandibles called a stylet. Some species of thrips are predatory, and may be deliberately released in cannabis grows to combat spider mites and other parasites, but the majority of thrips are phytophagous ("plant-eating") insects that feed on chloroplasts from epidermal and mesophyll cells on the surface of the plant.
Wikipedia article for general information on thrips:
https://en.wikipedia.org/wiki/Thrips