PRP stands for platelet-rich plasma. This is concentrated blood platelets in the patient’s own plasma. To create this, the doctor takes blood and spins it in a centrifuge to concentrate the platelets.
The idea behind PRP injections is that platelets have growth factors that they release to aid healing. So if you cut yourself, the platelets clot the blood and also release growth factors to help the cut heal. Hence, PRP can help injured tissues heal.