when you see a slash between the letters it is when there is a bass note that might not be in line with the actual chord being played. a common one is C/G. for the uke, since most of the notes are higher, trying to play a bass note isnt going to be as dramatic as say on a piano or guitar, where the is more lower range. so you would just play it as a C chord. if your uke is tuned with a low G, then it would be played:
3
0
0
0
since the lowest string is already a G note. but with re-entrant tuning, you can always just get away with playing the chord on the left like you would normally play it.
on a guitar, you would just play the C chord making sure that the lowest note is a G. on a piano, you could play an octave of G notes with your left hand while playing the C chord on your right hand.
a more difficult one would be a C/F. on a piano this would be easy, but on a stringed instrument, it makes it a little more difficult. like i said, you can always just get away with playing only the main chord (C in this case). but on a guitar, you would need to reach over with your thumb to depress the first fret on the low E string to make it an F while playing the regular C chord. on an ukulele, you would need to find where the F note on your 3rd string and depress that while somehow positioning the rest of your fingers on C,E,and G notes (a C chord) on the other three strings. this is a little worthless, because at that level you are already going be beyond the first 5 frets, and even though the lowest note is an F, it defeats the purpose of trying to get a bass note out of it.
so you just gotta see what you can do with each one. use the ones that will sound good, improvise with the ones that arent practical enough for the trouble.
"sus" chords are not something im comfortable explaining. i can play some of them, but they still confuse me on how they should be played. so ill let someone else explain that one.