It depends on what your background is.
#AI is a set of algorithms that enables a machine to reason about tasks. The 'reasoning' being the keyword.
Reference book + code: https://aima.cs.berkeley.edu/
Current #DL is the machine figuring out the reasoning by itself based on input/output. Another approach is model-based reasoning #MBR - an expert designs how the machine should reason.
Planning: https://planning.wiki/
Cognitive architecture: https://soar.eecs.umich.edu/