The Predefined Publishing Times feature allows you to determine in advance what time on each day of the week your posts will be shared, for each of your social accounts. Using it can be extremely handy and time saving since you won't have to establish a time for each post every time you schedule one.
When using this feature your posts will be scheduled to the first free Predefined Publishing Time slot of each account that you select. If you create and schedule a new post, it will be saved in the second free slot and so on.
Here is a tutorial on How to Set Up Your Predefined Publishing Times (Step by Step Guide!)