It is almost the same, but salve is more formal. If you meet someone who has the same age but is a work situation it's better to say "Salve".

it is the same, Ciao in italy is the greeting more used

if it's evening you can use "buonasera"

"salve" is not used so often, you can use "buongiorno" if you want to be formal or "ciao" with a friend or someone who is the same age of you

salve is more formal, ciao more informal