A model process consists of a tool and all variables connected to it. Connector lines indicate the sequence of processing.
There will often be several processes in a model, and they can be chained together so that the output from one process becomes the input for another process.
Each process in a model is in one of four process states: Not ready-to-run, Ready-to-run, Running, or Has-been-run.
When you initially drag a tool into a ModelBuilder window, the process is in a not-ready-to-run state (the tool is white) because the required parameter values have not been specified. The not-ready-to-run state means that the model cannot be run within ModelBuilder. If your empty data or value variables are exposed as model parameters, you can run the model by opening the model tool dialog box from the Catalog window or ArcToolbox window and specifying the model parameter values.
A process is ready-to-run when all required parameter values have been specified. Processes that are ready-to-run are symbolized in color; input data elements are blue, tool elements are yellow or orange, and output data (derived data) elements are green.
The process is currently running. Tools that are running are red.
If the model is run within ModelBuilder, the tool and output or derived data elements are displayed with drop shadows, indicating that the process has run.