In the context talked about in the OP, an elite are a group of people that have a larger/an ousized amount of power in a specific social context. So yes, business leaders, high-ranking politicians and very wealthy people are generally part of the elite in our society. Note that a 'social context' can be society at large, but also much smaller, the board of a HOA can form an elite in a small town for example. That social context can also be quite complicated: Trump famously was never really a part of the NYC wealthy elite, despite being a wealthy New Yorker, because he didn't fit in socially.

Elite can also mean a person or group of people that is better at something than others, there's some obvious overlap with the definition above, but it is less useful in the context of political elites, which we are mostly talking about in the context of Twitter.