Alavi is a surname that some people have. A surname is a name that people have that comes from their family, like a last name or a family name. So if your mom and dad have the last name Alavi, then you would have that last name too.
Alavi is a name that comes from Persia, which is a country that is now called Iran. It is a Muslim name, which means that it comes from the religion called Islam.
People have different last names because in the past, people would have last names based on what their job was or where they came from. For example, someone with the last name "Smith" might have ancestors who were blacksmiths, which is someone who makes things out of metal. So their name came from their job.
Some people with the last name Alavi might not know what their ancestors did for a living or where they come from exactly, but they still carry that last name as a family name.