A Gaussian calculation scheme is basically a named template for a Gaussian job.  A Gaussian calculation scheme can consist of a set of Gaussian keywords, a set of link0 commands, a title and possibly a set of additional input lines to follow the molecule specification.

Gaussian calculation schemes are especially useful for quickly and reliably setting up similar or identical calculations for a set of molecules, especially if the calculations involve a lot of non-default input.

The workflow in using Gaussian calculation schemes is typically as follows:

1. Load or build a molecule in a view window.
    
2. Assign a Gaussian calculation scheme to the molecule.
    
3. Save and possibly submit a Gaussian job file.

The value of Gaussian calculation schemes lies in step 2, which eliminates much or all of the time (and possibly error) spent manipulating controls in the "Gaussian Calculation Setup" dialog or manually editing Gaussian job files.