Pinyin is how Chinese sounds are written with Latin letters. Children learn it first, so they can read new words before they know the characters. This chart follows the school 拼音表: 23 initials (声母), 24 finals (韵母) and 16 whole syllables (整体认读音节). Tap a sound to hear it in four tones, with words to practise.
These syllables are read as one whole sound — you don't build them from letters.