If my a name has an "-" in between them what does that mean for example if the name is marco garcia-varela.?

In this case, it's two last names, Garcia being the father's surname and Varela being the mother's maiden name.

It depends on the person's ethnic background. Persons of South-American Spanish origin often hyphenate the family names of their mother and father. It's a way of letting people know your origins. In the United States, it was popular for a while to hyphenate the father's last name and the mother's maiden name. The outcome may be the same, but the intent is quite different, because this was a feminist/liberal idea of avoiding the "patriarchal" idea of naming the child after the father. The child's last name was actually (legally) Jones-Smith, and it was not assumed that the double name would revert to single in the next generation. A third option is the hyphenated British name, where an old family name (usually related to property) is kept along with the person's actual last name. So if I'm Jane Doe, the heir of the Landworth estate, I might call myself Jane Doe-Landsworth.

It depends on the person's ethnic background. Persons of South-American Spanish origin often hyphenate the family names of their mother and father. It's a way of letting people know your origins. In the United States, it was popular for a while to hyphenate the father's last name and the mother's maiden name. The outcome may be the same, but the intent is quite different, because this was a feminist/liberal idea of avoiding the "patriarchal" idea of naming the child after the father. The child's last name was actually (legally) Jones-Smith, and it was not assumed that the double name would revert to single in the next generation. A third option is the hyphenated British name, where an old family name (usually related to property) is kept along with the person's actual last name. So if I'm Jane Doe, the heir of the Landworth estate, I might call myself Jane Doe-Landsworth.

In this case, it's two last names, Garcia being the father's surname and Varela being the mother's maiden name.

Well, in America, a hyphenated last name is usually a woman's "maiden name" or birth name followed by her married name, so, if Jane Doe married John Smith, she could use the name Jane Doe-Smith if she wanted to, but in other countries it may be done differently. Good luck!... :-D