The difference between a onedimensional array and the twodimensional array is that onedimensional array store single list of elements of similar data whereas in twodimensional array list of lists or array of arrays is stored.
The array is a data structure that is very important in computer programming. In computer programming, array and structure are a very important concept. The array has elements of same data type and size in the array is also fixed. The array is declared with an array name and array is created with square brackets. Onedimensional array store single list of elements of similar data whereas in twodimensional array list of lists or array of arrays is stored
A onedimensional array is also known as a singledimensional array. There is a list of variables of similar data types. In onedimensional array elements are retrieved by using the index. If we talk about how memory is allocated to a onedimensional array, then it is allocated by defining the size of the array at the start of the code. Every programming language has its own way of defining array if we talk about C++ programming language then the onedimensional array is defined as type variable_name[size]; the size of the array is defined in the bracket. Size is the number of element that array will hold.
A multidimensional array is supported in C++ and Java programming language. A multidimensional array is also known as 2D array commonly. Onedimensional array se list of list and the multidimensional array is an array of array. There should be array name with square brackets where the second index is the second set of the square bracket. As it is 2D array, it is stored in the form of a rowcolumn matrix. In this rowcolumn matrix, the row is the first index and column is the second index.
Comparison Chart
Basis  OneDimensional (1D) Array  TwoDimensional (2D) Array 
Meaning  onedimensional array store single list of elements of similar data  In twodimensional array list of lists or array of arrays is stored.

Size  Size of onedimensional (1D) array is Total Bytes =sizeof(datatype of array variable)* size of array.  Size of twodimensional(2D) array is Total Bytes= sizeof(datatype of array variable)* size of first index*size of second index. 
Dimension  Onedimensional(1D) array is one dimension  Twodimensional (2D) array is two dimension. 
Row column matrix  There is no row column matrix in onedimensional (1D) array.  There is row and column matrix in twodimensional(2D) array 
OneDimensional (1D) Array
Onedimensional array is also known as singledimensional array. There is a list of variables of similar data types. In onedimensional array elements are retrieved by using index. If we talk about how memory is allocated to onedimensional array then it is allocated by defining size of the array at the start of the code. Every programming language has its own way of defining array if we talk about C++ programming language then onedimensional array is defined as type variable_name[size]; size of the array is defined in bracket. Size is the number of element that array will hold.
TwoDimensional (2D) Array
A multidimensional array is supported in C++ and Java programming language. A multidimensional array is also known as 2D array commonly. Onedimensional array se list of list and the multidimensional array is an array of array. There should be array name with square brackets where the second index is the second set of the square bracket. As it is 2D array, it is stored in the form of a rowcolumn matrix. In this rowcolumn matrix, the row is the first index and column is the second index.
Key Differences
 Onedimensional array store single list of elements of similar data whereas In twodimensional array list of lists or array of arrays is stored.
 Size of onedimensional (1D) array is Total Bytes =sizeof(datatype of array variable)* size of array whereas Size of twodimensional(2D) array isTotal Bytes= sizeof(datatype of array variable)* size of first index*size of second index.
 Onedimensional(1D) array is one dimension whereas Twodimensional (2D) array is two dimension.4
 There is no row column matrix in onedimensional (1D) array whereas there is row and column matrix in twodimensional(2D) array
Conclusion
In this article above we see the clear difference between the onedimensional array(1D) and twodimensional array(2D) with implementation.