Vectorization is a powerful ability within NumPy which is used to speed up the code execution without using loop. It expresses operations as occurring on entire arrays rather than their individual elements.
Looping over an array or any data structure in Python has a lot of overhead involved. In NumPy, Vectorized Operations delegates the looping internally to highly optimized C and Fortran functions, making for cleaner and faster Python code. So, vectorization refers to the concept of replacing explicit for-loops with array expressions, which can then be computed internally with a low-level language, like C.
Read on for a few examples of this and broadcasting.