Off topic:indication of N's sequences in reference genome

Question

[Nelislam4]

Hi,

I just wanna know. What is the function of N's sequences in any reference genome? What is the indication of them in the reference genome?

When I've searched about it in the README file of Human Reference Genome of Ensembl, I found that it's masked sequences because they are repeats in the genome!

Is that right for any genome reference of any organism?

Thanks in advance, Nour