When it is required to state the topic of the sentence for clarity, the particle (は) is used, but it is not required when the topic can be inferred from context. Also, there are frequently used verbs that imply the subject and/or indirect object of the sentence in certain contexts: (くれる) means "give" in the sense that "somebody other than me gives something to me or to somebody very close to me." (あげる) also means "give", but in the sense that "someone gives something to someone other than me." This often makes pronouns unnecessary, as they can be inferred from context.