Breakfast consumed after the first breakfast which is eaten very early in the morning, or early in the day in the process of a long journey. The first breakfast is usually light in nature and consists of small portions.
When I woke up early in the morning at 7am to watch cartoons my mother hadn't made breakfast yet so I just had a little bit of cereal. When she woke up at 9:30am she made me bacon and eggs, which was my second breakfast.
When I went camping with my friends they got drunk the night before so early in the morning I just had a small breakfast before they awoke so that we could all eat breakfast together later. My first breakfast consisted solely of biscuits. While for second breakfast I ate bacon and eggs. The breakfast I ate with them was second breakfast.