This is the 656th most frequent French word.
humanitaire
Relating to humanitarian aid or concern for human welfare.
In this case, "humanitaire" functions as an adjective describing the work, indicating that it is related to providing aid or support to improve human circumstances.
Le travail humanitaire peut être gratifiant mais éprouvant.
Humanitarian work can be rewarding but challenging.
Finally, "humanitaire" modifies "action," portraying the nature of the activities as directed towards humanitarian efforts and goals.
Elle a choisi de se consacrer à une carrière dans l'action humanitaire.
She chose to dedicate herself to a career in humanitarian action.
Here, "humanitaires" is used as an adjective describing the organizations, emphasizing their humanitarian nature—focused on human welfare.