The word literally means "my son", but it's rarely used in its literal sense.
Here are some examples:
* "Mijo, ¿cómo estás?" (My son, how are you?)
* "Ven aquí, mijo." (Come here, sweetheart.)
* "No te preocupes, mijo." (Don't worry, dear.)
It's important to note that "mijo" is a colloquial term and might not be appropriate in formal settings.