A phenotype, usually shortened to "pheno," is how a particular plant's genetics actually show up in the real world: its height, bud structure, color, smell, yield and chemical profile. When a breeder pops a pack of seeds from the same cross, each seed can grow into a slightly different plant. Each of those is a different phenotype.
Breeders and growers go "pheno hunting" by growing many seeds from the same cross and picking the one or two plants with the best traits. They then keep that plant alive by taking cuttings (clones), so every future plant is a genetic copy. You will sometimes see a pheno noted on a label, like "#4" or "the purple pheno."
This is part of why the same strain name can look and smell different from one grower to another. One farm may be growing a gassy phenotype while another grows a fruitier one. The environment matters too: light, nutrients, temperature and curing all shape the final result.
For shoppers, the practical takeaway is simple. If you liked a product, note the grower and batch, not just the strain name. The batch's lab report will tell you more about what you got than the name alone.