Endocannabinoid receptors are like little locks on the surface of your cells. They are there to receive signals from endocannabinoids, which are like the key that fits into the lock and opens it. When the endocannabinoid binds to the receptor, it causes a change inside the cell, which can have different effects depending on which receptor it binds to and where it is in the body. There are two main types of endocannabinoid receptors: CB1 and CB2. CB1 receptors are found mostly in the brain and nervous system, while CB2 receptors are found in the immune system. When you use cannabis or other products that contain cannabinoids, these compounds can also bind to these receptors and cause changes in the body. It's kind of like using a fake key to open the lock - the cannabinoid acts as a stand-in for the endocannabinoid.