Greetings are a key part of Italian and unlike English, formality is common in Italian. We have it in English, but it is not so strict. Saying Hi vs Hello in English is not that big of a deal.
Ciao and Salve both mean hello but are used based on how well you know who you are speaking to. Ciao can also mean goodbye.
Ciao
[chow]
hello (informal) - use with people you know like family and friends.
goodbye (informal) - also with people with you know. you may here "ciao ciao", which is also goodbye
Salve
[SAHL-veh] - "SAHL" rhymes with "hall" and "veh" is a soft "e" sound, like in "bet"
hello (formal) - use with people you don't know. it is formal and neutral.
The formality of salve is in between the formality of Ciao (informal) and Buongiorno (formal).
Buongiorno means "good day" or "bood morning" and is a more common formal greeting than Salve. use buongiorno during the morning and early afternoon.
There a several Italian greetings, but knowing the difference between Ciao and Salve is a good introduction into the Italian culture.