Discretizing the domain into a grid.
If you are interested in learning more about computational methods for PDEs, we recommend the following resources: Discretizing the domain into a grid
by M.K. Jain is not legally available for free download due to copyright, you can access the textbook or similar core material through several legitimate platforms. Textbook Details Computational Methods for Partial Differential Equations M.K. Jain, S.R.K. Iyengar, and R.K. Jain Publisher: New Age International Publishers Discretizing the domain into a grid