Japanese readings - On’yomi & Kun’yomi Japanese kanji have two different readings (or ways to pronounce them). There's on'yomi readings and kun'yomi readings. On'yomi is based on imported Chinese words. Kun'yomi is based on native Japanese words.
Each kanji can have multiple on'yomi and/or kun'yomi readings. Or, a kanji may have just one reading, either on'yomi or kun'yomi. The kanji for rice is 米. It has all the following ways to read/pronounce it: On: ベイ、 マイ、 メエトル Kun: こめ、 よね *Because the on'yomi is the Chinese reading, it's usually written in katakana (which is the writing system used for foreign words). (Very) Quick History - Kanji came over from China a long time ago, before Japan had a writing system. It was adopted as a writing system, but Chinese and Japanese sound really different, hence the different ways to pronounce kanji. I found a pretty good article explaining why some kanji have only a kun’yomi reading, or why there are multiple on’yomi readings, etc. Click HERE for that. There are some general rules that might help you know when to use the on vs kun reading. For example, kanji with hiragana attached (like 飲みます) often use the kun'yomi reading. Multi-kanji words (like 東京) often use the on'yomi reading. But there always seem to be exceptions so... Studying, practice, and then finally experience are probably going to be your best ways to learn when to use which reading. EXTRA There's also Nanori readings (名乗り) which translates as "self-introductions". These readings are used almost exclusively for Japanese names.