About distribution from a trust [View all]

If a trust fund is paid out, how do you figure out if you have to pay any taxes on it? I was reading about trusts funds and I understand that I wouldn't have to pay taxes on principal, but would have to pay taxes on interest or other income the money generated. If I get an amount of money from a trust, how is it determined what is principal and what is income?

I am curious about the methods, but I don't have the education to comprehend how the calculations are made.

Thanks fot any insight.