A computer program is nothing more than an algorithm that is written in a language that computers can understand, like PHP, C++, C#, or Java.
A computer program cannot actually make you a cup of tea or cook your dinner, although an algorithm can guide you through the steps to do it yourself. However, programs can (for example) be used to calculate the average value of a set of numbers, or to find the maximum value among them. Artificial intelligence programs can even play chess or solve logic puzzles.