Often data comes naturally in two dimensional form. Web browser screens are two dimensional, as are spreadsheets, printed pages, and images.
For many of these situations you need a two-dimensional array. This is a collection of cells laid out in a 2D grid, like graph paper. Each cell can hold a value (as with a 1D array). However, now two indexes are needed to specify a cell.
If you have ever used a spreadsheet then you have used a 2D grid for holding and manipulating data.
One programming problem in the 2014 Advanced Placement test for computer science required use of a two dimensional array of object references.
(Thought question: ) Do you suspect that 2D arrays in Java are objects?