Why are ethidium bromide or Sybr Safe stains able to be used

Why are ethidium bromide or Sybr Safe stains able to be used to estimate relative DNA concentration in a gel?

And

How are ethidium bromide, Syber Safe stain, and Sypro stains similar?

Why are ethidium bromide or Sybr Safe stains able to be used to estimate relative DNA concentration in a gel?

And

How are ethidium bromide, Syber Safe stain, and Sypro stains similar?

And

How are ethidium bromide, Syber Safe stain, and Sypro stains similar?

Hi,

I hope my answer is satisfactory.

Thanks!!