Dynamically Populating Label Parameters
You can provide a string with placeholders, which are replaced by the substitution values at runtime.
Add as many parameters as you need. The parameters are numbered and are zero-based. For example, if you have three parameters, they will be named {0}, {1}, and {2}, and they will be substituted in the order they're specified.
Let's look at a custom label, $Label.mySection.myLabel, with a value of Hello {0} and {1}, where $Label is the global value provider that accesses your labels.
This expression dynamically populates the placeholder parameters with the values of the supplied attributes.
{!format($Label.mySection.myLabel, v.attribute1, v.attribute2)}
The label is automatically refreshed if one of the attribute values changes.