All of autosomal genetic genealogy is based on these concepts of inheritance and matching, so if you don’t understand these, you won’t understand your matches, how they work, why, or how to interpret what they do or don’t tell you.
This article provides an excellent, illustrative overview of DNA inheritance from one generation to the next: http://dna-explained.com/2016/02/25/concepts-how-your-autosomal-dna-identifies-your-ancestors