This is the 1573rd most frequent French word.
organiser
To arrange or plan systematically.
In this sentence, 'organiser' is used in the context of planning and arranging an event, specifically a birthday party.
Je vais organiser une fête d'anniversaire pour mon ami.
I am going to organize a birthday party for my friend.
Here, 'organiser' refers to the act of arranging or categorizing items, in this case, books by their color.
Elle aime organiser ses livres par couleur sur les étagères.
She likes to organize her books by color on the shelves.
In this example, 'organiser' is used to mean structuring or sorting abstract concepts such as ideas to prepare for a task.