Many electrical drawings consist of groups of devices chosen to work together. Devices such as a filter or an amplifier and maybe an analog to digital converter. To make sense of some drawings it is best to recognize some of these devices in order to understand how they work. For that level of understanding, you must study at the college level for at least 2 or 3 years and then you need to build upon that learning.

Digital circuits are like building blocks. There are many ways you can combine them to achieve different functions. To design, you start with the desired function and then work toward the required digital circuits to achieve it. There are usually several alternative solutions to the same problem.