In
English and most other
languages (including
Japanese),
independent clauses are linked together by
conjunctions, such as "and", "or", "but", etc.
Subordinate clauses (the other type) cannot stand on their own and are linked with words like "because" or "so".
Independent clauses can be separated and still retain the same meaning. Subordinate clauses become fragments when separated from their subordinating clauses. A common grammatical error in English.