In social sciences, the term "social opportunity" is generally used to refer to the idea that people have different opportunities based on their social networks and the overall environment in which they live. So, if I talked about my social opportunities, I would be talking about the ways in which who I know and where I live can affect what opportunities I might have.
So, for example, a social scientist might ask about the way that social opportunities affect education. They might focus on the whole context of schools and ask whether/how much schools can help kids when everyone they know is uneducated and doesn't value education.
I agree with the first response, but I would like to add several other examples. When a child grows up in a neighborhood such as the Greasers in the book "The Outsiders," the social opportunities that surround him/her are limited by the surrounding environment. Let’s say that all the children in his classes also live in the rough environment, the child is less likely to have outside contacts that would help him to develop differently than from those around him.
While there are exceptions to the rule, generally the people who move into prominent positions are often equated to a position relative to his social opportunity. If a student graduates from Harvard he/ she is usually exposed to opportunities that the child from the poor rough neighborhood. It does not mean the person is any better; he is just in the advantageous social vicinity that leads to social opportunity.