it talks about someone who is doubting their life and existence. they would like to know why things change and happen in life. Thhat person dosn't want ot live like that anymore as they have had enough. they wish they could switch bodies and get away from th ehardness of life. This song also represents a story that leads off to suicidal thoughts and suicide itself. In the first verse, when it says 'pourquoi je vis, pourquoi je meur' it represents the thought that someone might have about why even bother live if you are going to cry anyways. There are lots of oppisite sentences meaning that for example, why laugh then cry or why dark then bright. when it refers to them wanting to leave earth and become a bird it means to be free and do whatever they want and to be able to see life from another perspective or point of view. There are a few little sentences easy to spot but a big meaning hiding behind them, for example 'dodo l'enfant do' can either mean to enjoy life at young age as thhere is complicated stuff ahead or dodo might mean sleep which means death in a sad way. i hope you liked my explanation, my grandpa taught me it when i was younger cause they are friends with the young (dead now) singer 'gregory lemarchal's ' grandparents!