Most know what I am like,
and yet some never will.
Many objects possess me,
but those you think do, do not.
I have many siblings,
and if you know me, you'll know 5 of them.
Maybe you know of the other ones,
but even then, you will never see them.
My name does not contain the letter D,
But I share my name with something that does.
And I have no physical form,
and yet you see me every day.
What am I?
Answer every line of the riddle in your answer for it to be counted correct