The literal translation of nǐ hǎo (nee how) - 你好 is "you good". Nǐ - 你 means "you" and hǎo - 好 means "good".
Nǐ - 你 is the informal form of "you" and is used for greeting friends and associates. The formal form of "hello" is ►nín hǎo (neen how) - 您好. Notice that the formal "you" is nín - 您.
Use nín hǎo - 您好 when speaking to:
People in authority
Use nǐ hǎo - 你好 when speaking to:
China & Taiwan
The use of nín hǎo - 您好 is more common in Mainland China than in Taiwan. The informal nǐ hǎo - 你好 is the most common greeting in Taiwan, no matter what the rank of the person you are addressing.