Let us suppose you got fresh leads to cold call. There are 10 such data that you have got at 10 am on 1st July, 2018. You called all of the 10 people at 11am. I wish you will agree that all these 10 people would not pick your call on the first attempt. Let us assume that 4 people picked your call. Now for the remaining 6 people , your manager has asked to follow these leads 3 hours later again. In order to remember that you have to call all these 6 people back, you have to create task for all these 6 people that can remind you to follow up 3 hrs later. Otherwise you will forget to call them back. 

Now imagine if you have created a step in the campaign after a gap of 3 hrs. The software will automatically create the task for these 6 people and will remind the sales rep that these 6 calls are due.  So no need to create task. The software automatically reads that the call has been answered or not and based on that it creates task automatically. 

Please find the below image. In the below image you can find that you have two steps. The first Step is Day 0 ( 0 Hrs, 5Mins). It means that the first step will be Due 5 mins after the data is added to this step. 

In the Second step, you will see that it has, Day 1 (0 hrs, 5mins). It means one day later, on Day 1 after 5 mins data will be added to second step.