This is mainly divided into two situations ~
1. The verb itself has two parts of speech: self and self.
2. Omit the object in the sentence.
Especially the latter, it often happens, because Japanese is a vague language ~ When the topic of conversation is something that both sides know, it is often omitted ~
Chinese is also like this ~
For example: Have you eaten? (only verbs have no object ~ omit the object rice)
ごまで ~