A focused corner of biology
Biology is the whole study of life — anatomy, behaviour, ecology, physiology, cells, and more. Genetics is one focused corner of it, with a defining question all its own: how is information passed across generations, and how does it shape what organisms are? You can study a frog's anatomy without genetics, but the moment you ask why this frog differs from that one, or why its tadpoles resemble it, you have stepped into genetics.
Genetics sits especially close to cell biology, because the genes it studies live inside cells, packaged on chromosomes. But the two have different centres of gravity. Cell biology asks how a cell works as a living machine; genetics asks what information the cell carries, how that information varies, and how it is handed on. They share a building — the cell — but they look at different things inside it.
Genetics and genomics
You will often see genetics paired with a younger relative, genomics. The two are easy to tell apart once you have the right image. Classical genetics tends to follow one gene or a few genes at a time — tracking how a single trait is inherited, as we did with eye colour. Genomics steps back to study a genome as a whole: all the genes, all the DNA, and how they behave together, usually with the help of computers and large datasets.
Put simply, the distinction genetics vs genomics is mostly one of scope: a few genes versus the whole genome. Neither replaces the other. Genomics gives a wide map; classical genetics still tells you how a particular trait travels through a particular family. You need both to see the full picture.
That rounds out the foundation. You now have the core vocabulary — gene, allele, heredity, variation, genotype and phenotype — and a sense of where genetics sits among its neighbours. Everything more advanced, from Punnett squares with two genes to the reading of DNA itself, builds on exactly these ideas.