Something is articulated if it's made of sections connected by joints. Articulated limbs have bones that bend where they join, at an elbow or a wrist for example.
Human bodies are full of articulated sections, with joints at the knees, hips, shoulders, and so on. You can also describe an object as articulated if it's made up of pieces that connect in flexible segments. A long train can be composed of articulated cars. Articulated comes from the verb articulate, "to divide into distinct parts," from the Latin articulare, "separate into joints," and the Latin root articulus, "joint."