Reading circuit diagrams involves understanding the symbols and connections used to represent electrical components and their interconnections. By analyzing the diagram, one can identify the components, their functions, and how they are connected to form a circuit. PLC programming involves writing logic using a programming language such as ladder logic or structured text to control the operation of a programmable logic controller (PLC). This includes defining inputs and outputs, creating rungs of logic to perform desired tasks, and implementing control algorithms to automate processes.