Hello! That is often referred to as a C5 chord, which means that it is just a root (C) and a fifth (G), or in this case 2 of each. This type of chord is sort of like a "power chord" on a guitar, which also contains a root and fifth, but it sounds quite different on uke. It is a fairly neutral sound since it contains no "third" which is the note that gives a 3 note chord (triad) it's "quality (major, minor etc....).
Anyhow, I think most people use this as an option if a C major chord is called for but they desire a slightly different sound.
Hope that helps!!!!!!