Both yomi(read / how to pronouce) are ways to pronouce Kanji. On-yomi: Basically pronoucing as Chinese. Just sound in Japanese. A long time ago, Kanji came from Chinese with their pronounce. Kun-yomi: Ancient people read kanji with Japanese language already exist. That's Kun-yomi. Example: 「音」 means sound. In on-yomi, pronounce as ね or おん. In kun-yomi, pronouce as おと. Basically, On-yomi has no meaning just a sound, They have no meaning themselves. On the other hand, Kun-yomi has meanings. I hope you can understand. I should study English more :-)

usualy on-yomi is written in katakana, while kun-yomi in hiragana

in my opinion，that，おんよみ is comes from chinese pronunciation；and くんよみ is 日本語のpronunciation；so official word used to useおんよみ，usual word used to use くんよみ。i‘m learning japanese now，i used to remember the whole word，for example　 ”食”の　おんよみ　is “しょく” ［食卓（しょくたく）］；“食”の　 くんよみ 　is ”たべる”「食べる」；　and i think is much easier for u to remember that two words［食卓（しょくたく） and 食べる］than u just remember ”食”の　おんよみ　is “しょく” ；“食”の　 くんよみ 　is ”たべる”。 please forgive my poor english。

There is no need to worry about it at this stage. In a few weeks the whole thing will become obvious. Be patient. A short tip. Study the meaning and writing first, then study the readings. This called the Heisig method. In fact, get his book: Heisig: Remembering the Kanji. There is no need at this stage to make special efforts to learn the readings. You can pick most of them up quite naturally as you progress in your Japanese. Good luck.

hehe, well basicaly yes it is. Though sometimes it's difficult to find proper reading of a word. Even knowing that kun is for single kanji reading, on for compound reading. Multiple readings and exeptions makes it hard.