In order for you to prioritize your tasks and get the right things done at the right time, you need to focus.
To set a Follow up on a task, either edit the task, and choose an exact day to Follow up that task or from the List view swipe from left to right to Follow up in 1, 3 or 5 days. You can choose to view your Follow up tasks or not, by toggling View Options - more on View Options here.
An example of how Follow up could be useful is if you have written a blog post and need your colleague to proof read this, you don't want to complete the task as the blog post isn't posted yet and you want to check that your colleague has proof read this in 3 days time, you can choose to follow up that blog post task either by swiping 'Follow Up in 3 days' from the List view or edit the task to choose an exact follow up date.
Now that the task is off your list so you can focus on more pressing tasks and you can relax knowing that Gneo will bring that task back into your list in 3 days to remind you to follow up with your colleague!