When speaking English, you know the importance of placing the accent, similarily the Chinese use 5 tones to dictate the raising and dropping sound in speech. While people are familiar with the tones, seems only a few familiar with the "tone marks", as red symbols shown in the sentences below, and the table follows:


As shown in the table above, tone marks for the second, third, and fourth tones are shared between bopomofo and pinyin. In bopomofo, the first tone mark is usually omitted but can be included, while a dot above indicates the fifth tone (also known as the neutral tone). In pinyin, a macron (overbar) indicates the first tone and the lack of a marker usually indicates the fifth (light) tone.
Hope this helps.
https://en.wikipedia.org/wiki/Bopomofo