1. The document discusses bastidores (frames) and máquinas (machines), which are structures composed of members connected by pins that experience multiple forces. 2. It explains that frames are generally stationary and support loads, while machines contain moving parts and are designed to transmit and alter the effect of forces. 3. The document provides steps for determining the forces at joints and supports of frames and machines, which include isolating each part, identifying two-force members, and representing equal and opposite forces on contacting members.