Q: Practically speaking, what is the difference between arrays and pointers?
A: An array is a single, preallocated chunk of contiguous elements (all of the same type), fixed in size and location. A pointer is a reference to any data element (of a particular type) anywhere. A pointer must be assigned to point to space allocated elsewhere, but it can be reassigned (and the space, if derived from malloc, can be resized) at any time. A pointer can point to an array, and can simulate (along with malloc) a dynamically allocated array, but a pointer is a much more general data structure (see also question 4.1).
Due to the so-called equivalence of arrays and pointers (see question 6.3), arrays and pointers often seem interchangeable, and in particular a pointer to a block of memory assigned by malloc is frequently treated (and can be referenced using ) exactly as if it were a true array. See questions 6.14 and 6.16. (Be careful with sizeof; see question 7.28.)
See also questions 1.32, 6.10, and 20.14.