Where can I find out more information about Global Development Delay?

My 6 year old niece was diagnosed with global development delay when she was about two years old, but I don't know anything about as I haven't heard of global development delay until my niece was diagnosed with it. She's a happy, healthy little girl although she's non-verbal.
My youngest sister(my niece's mum) and her wife (who herself and my youngest sister and the rest of our family call momma to my niece,) are trying to raise funds for a piece of equipment which is called an eye gaze which is used by my niece's special school so that the teachers know what my niece wants and needs whilst she's in school, for at home so that my youngest sister and her wife know what my niece wants and needs at home too with my niece being non-verbal. My niece can sign as she signed "happy birthday" to her nana (mine n my youngest sister's mum) (we have another sister and a brother) last October as her momma picked her (my niece) up from her (my youngest sister's wife's mum's and stepdad's place) and decided to nip to my mum's on the way home to wish my mum happy birthday.