Solar panels sit at the heart of a photovoltaic system, converting sunlight directly into electrical energy. But a panel is itself an assembly of smaller units — the vocabulary helps when reading specifications.
The cell
The smallest building block is the photovoltaic cell, a thin slice of semiconductor — most commonly silicon — treated to create the electric field described in The Photovoltaic Effect Explained. Each cell absorbs photons from sunlight and produces a small direct current at a small voltage.
The module
Because one cell produces little power, manufacturers wire many cells together in series and seal them behind protective layers — tempered glass on the sun-facing side, a durable backsheet behind — framed in aluminum. The finished assembly is a module, which is what most people mean by a solar panel. Typical modules contain 60 or more cells.
The array
Modules are mounted on racking and wired together into an array. Arrays range from a handful of modules on a house to thousands in a utility-scale field. Wiring decisions — how many modules per string, how strings are combined — are part of system design and must match the inverter's specifications.
What the materials do
Silicon does the energy conversion. The glass and backsheet protect the cells from weather, moisture, and mechanical stress for the decades a module is expected to serve. The frame provides structure and a way to attach the module to its racking. Every layer exists to keep the fragile cell doing its job, year after year.