A few basic Kanji questions

Ok, this seem like it may be fairly stupid question, but I couldn't find an answer for it anywhere. Do the on-yomi and kun-yomi of each Kanji have the same meaning? I mean I know they're different words, but for instance, 木's kun-yomi is き, which means tree. Does this meaning only pertain to the kun-yomi, or do all the on-yomi (ボク, モク) also mean tree? I'm thinking not and that the on-yomi is more just ways to string sounds together to make a word, but I'm not sure and would really appreciate some help with this, provided I'm making any sense at all, haha.

the meaning of a kanji by itself never changes, but like the way it is read, it can vary when used in different words and compounds. Generally, you can expect words with 木 to have something to do with trees.