the netlist
If a schematic is a picture of a circuit, a netlist is the same circuit written down as plain text, the way a recipe lists ingredients and how they join. It is the actual language SPICE reads. Every line names one component, says which points it connects to, and gives its value.
Each connection point is called a node, and you give every node a name or number. A line like 'R1 in out 10k' means: a resistor called R1, connected between the node named in and the node named out, with a value of 10 kilohm. 'C1 out 0 1u' is a 1 microfarad capacitor from node out to node 0. 'V1 in 0 9' is a 9 volt source from in to node 0. SPICE reads these lines, works out which components share a node, and assembles the equations. When you draw a schematic in a graphical tool, it quietly generates this netlist for you behind the scenes.
Two components are electrically the same point only if they sit on the same node name. The classic beginner bug is a typo that puts one component on node out and another on node ouut, leaving a wire dangling and the circuit broken in a way the picture would never show. Reading the raw netlist is a fast way to confirm the simulator sees the circuit you meant.
A complete divider netlist is just four lines: 'V1 in 0 9', 'R1 in out 10k', 'R2 out 0 5k', and '.op'. Three components, three nodes (in, out, 0), and one command telling SPICE to find the operating point.
The entire circuit as text: components, the nodes they share, and an analysis command.
Node names are just labels; what matters is which components share one. A misspelled node name silently creates a separate, unconnected node, a mistake invisible in a schematic but obvious in the netlist.