During colloquial conversation, what is the difference between calling one first name or last name? I assume one if colloquial and one is more formal but not sure. Thank you very much!
The use depends a lot on the specific cultural and sub-culteral norms. For example, in the U.S. (even more so in California, but these days much of the country) given names are widely used in many contexts. In many companies or organizations, even lower-level employees address and refer to more senior employees by first name. This started in high-tech companies but has now spread widely. However, in much of Europe and the U.K., only good friends do this, or people of more senior rank do this to people of lower rank. There is also a tradition in some sub-cultures of addressing acquaintances by family name only (no honorific), while in other cultures this would be considered rude.
Generally speaking, we use a person's given name when we are friendly with, or close to, the person. Or if we are addressing a junior, for example an adult addressing a child, or a manager addressing a worker.
We use rather than an honorific, or a title and family name (known as a surname), in the opposite cases.
Acquaintanceship, or addressing a senior, such as a child addressing an adult or a worker addressing a manager.
As time goes on, in the UK, it is more and more common for children to address adults by first name, for example when addressing one of their friend's parents.
In the West, family names are generally the last name. In many parts of the East, family names are generally the first name.
This reflects two different traditions and outlooks.
One in which you are the named person, and you have a supplementary name to distinguish you from all the other people with the same name.
I'm John [the] Fletcher (someone who make arrows for a living) I'm John, Michael's son. I'm John [with the] red[ ]beard.
The other tradition has you as a member of a family, who can be distinguished from the other members of that family, if need be.
Who is that? It's Hayao. You know, the elder one - Hayao Miyazaki. Not the younger Hayao.
This can cause cross-cultural mis-matches. A senior engineer from Scotland, working in Thailand, was constantly referred to as "Mr. Jim" by the respectful local workers. "Jim" is a diminutive and so is an even more casual, friendly or intimate form of his given name, "James".