Breaks may only appear in specific slots that you will have to define in advance (e.g. in a simple scenario: every half hour). The slots are scheduled at specific time during a day where the break item(s) will fit in. The duration of the slot depends on the duration of the break items that it will contain. The break slots will be the same for everyday of the week although you may not use them all for each day (you can leave some of them empty).
The break items are used to configure the tracks played in each break slot. You may define the tracklist that will play on the break, the time period, tags that categorize it and fill the break item into the specific slots during the week. View all your break items together in the overview section.