In a junctional nevus, the melanocytic nests form at the dermal-epidermal junction.
The nevomelanocytic nests are discrete and located at the tips of the rete ridges
Melanocytic nevus also known as a "mole" have many variants and descriptions. Junctional nevus is a term used to describe melanocytic proliferation limited to the dermal-epidermal junction. Intradermal nevus have melanocytic nests located entirely within the dermis and compound nevus have nests located both in the dermal-epidermal junction and dermis.
Junctional nevus is usually seen as a brown macule clinically, whereas an intradermal nevus is a fleshed colored papule, and a compound nevus is a brown papule. This makes sense based on their depth.
Rapini RP.Practical Dermatopathology. Philadelphia, PA: Elsevier; 2005: 263.