I am really interested in learning computing, there is a program called React that is for building user interfaces.
How long has React been around?
It has been around since 2013 and aims to provide speed, simplicity, and scalability
I wish I knew more about building interfaces.  Would you recommend any other programs for a beginner?
I am just learning so for no all i know is React which allows people to create large web applications with ease. 
Where did React start up?  In the US?
Yes it was created in the US but is currently maintained by Facebook and Instagram
Is it used for smartphones too?  Or computers?
Yes there was a new version that came out in 2015 that enabled it to be used on Android, iOS and UWP
Sounds like it could be a really user friendly option!