Is tobi really obito?

as far as i know tobi is obito because when tobi got crushed zetsu being able to fuse with earth saved obito from the crushing rock and during the fight between jiraiya and pein were fighting and then they said u have to go through all of us so itachi got infront of pein he got hit in the ribs by kakashis lightning blade so then behind itachi was tobi he gave kakashi a hint of who he was kakashi fought him and he told his story of how he lived through the crushing blow of the gigantic boulder.(I dont know if it is completely true or not but thats what i think it is i dont really know thats why i am making this question)