So, to recap: on-readings are typically used when a kanji forms part of a compound word (usually a noun); kun-readings are normally used for single kanji, either as words in their own right, or as the stems of adjectives or verbs. Adjectives and verbs typically consist of a kanji followed by a hiragana suffix.

Beware: there are exceptions to this rule. Most kanji have at least one on-reading and one kun-reading each, but plenty have no kun-reading and a few have no on-reading. Some use kun-readings, not on-readings, to make compounds. You just have to learn them case by case.

1) given in capitals
2) used to form compounds
3) based on Chinese pronunciation

1) given in lower-case
2) used individually as nouns
3) used as adjective and verb stems with hiragana suffixes