When you tap on to add a new task, you will see suggested actions appear below the text box. These are 'action icons' and are there to help automate your task for you. If you write (or tap) an action word like call, text or email and then write the name of one of your contacts in your device, an action icon will appear on the right of your task. Pressing this icon will perform the action you have written in the task. For example, if you write "Call Mom", pressing the action icon will call Mom. But if you write "Email Dad", it will create an email with Dad as the recipient, but it won't write anything in the email or send it for you.
Please note that on iPad the call action icon is not applicable but as long as your email and text messages are set up to your iPad, they will work.