A lead or shoot can have any number of tasks (also referred to as reminders). A task is a great way to remind yourself to do something for a lead or shoot (i.e. send an email, post a photo on social media, call the client, etc.)
A task can have a due-date, which is how you'll likely use tasks most often. A task can be created without a due-date if you'd like a more generic task that isn't bound to a date, though.
How to add tasks to a lead or shoot
There are three ways to manually add tasks to a lead or shoot:
Go to the Lead > Overview page, click the "Quick Actions" button at the top of the page, and click the "Create Task" button.
Go to the Lead > Tasks page and click the "Add New" button at the top of the page.
Apply a workflow to the lead or shoot, which is a great way to bulk-add tasks that you create in a workflow template.