It literally translates to "How are you?", but it is used as a casual greeting similar to "hi" or "hello".
Here are some other Tagalog greetings you can use:
* "Magandang umaga": Good morning
* "Magandang hapon": Good afternoon
* "Magandang gabi": Good evening
* "Kumusta ka?": How are you? (more formal than "Kamusta?")
You can also use "Hello" as a greeting in Tagalog, as it is widely understood.