Functions or methods are a pre-written small set of instructions that result in a specific task being performed when they are called. The functions can also be defined as a single name for a group of programming instructions written together to achieve a common task.

Taking an example, think of driving as a function. In driving, there are multiple things that need to be taken care of, such as understanding traffic signals, running a car, and driving the car in traffic and on the road.

All these tasks are grouped in a function named driving. Now, let's say we have two people, example 1 and example 2, who want to learn to drive. From a programming perspective, once we define a function, we need to call it whenever we want to perform the same set of tasks. Hence, we would call driving(example 1) and then driving (example 2), which would ensure that both people would become a driver after going through the set of instructions in the driving function.

Let us look at another example:

countries=["India","China","USA","UK"]

function hellocountry(countryname)
 Return "hello " countryname

for each country in countries:
     hellocountry(each country)

In the first line, we declare an array with country names as elements. Next, we define a function named hellocountry that accepts an input of countryname. In the function itself, we simply return the value of the countryname that was passed to the function as input, preceding by the work hello.

Now all that remains is to iterate through all the elements of countries and pass each countryname as input to the hellocountry function. As we can see, we called the same function for each element, and based upon the instructions declared inside the function, that specific task was now performed for each element in the array.