Many PCB board markings are self-explanatory, R = resistor, C = capacitor, D = diode. But there are also many obscure PCB markings, such as U = integrated circuit, L = inductor, Q = transistor. That being said, I found a StackExchange question with a good reference for these marking abbreviations.
20191127/DuckDuckGo Q2 PCB marking
20191127/https://electronics.stackexchange.com/questions/25308/what-do-the-pcb-markings-mean
20191127/https://blogs.mentor.com/tom-hausherr/blog/tag/reference-designator/
Also, it’s something to keep in mind if you design your own printed circuit boards, what markings you should use for the components on your board.