two of, both of

[NIN]

Hello, teachers:
I am wondering what's the difference between "two of "and "both of" to native speakers.
Ex:
1 Two of the students are from the USA.
2 Both of the students are from USA.

Could you please help me to figure it out?
Thanks a lot!

[Marius Hancu]

1 Two of the students are from the USA. [Two of the total number of students, which can be anything equal or higher than two, are from the US

2 Both of the students are from USA. [The total number of students in this discussion is only two. Each of them is from the US

[NIN]

Thanks for Marius Hancu's clear clarification.
You always help me a lot!Thanks!:)