People who work in investment banking are usually grouped based on their function (M&A, IPOs, etc) or industry focus. When you join a bank for an internship or a full-time position, you could start as a generalist or join a team that focuses on a specific industry. The HR staff tends to ask newcomers if they have any industry knowledge/experience or preferences. One could even submit an ordered list with his/her preferences (e.g. 1 - Technology, 2 - Energy ...., 5 - Government).

The data shows that Financials is the hottest industry at the moment but there is no guarantee that this will continue forever. When I was a university student and I was trying to break into investment banking I focused mostly on FIG (Financial Institutions Group) since it was my favorite. I guess that today Technology is quite popular among students and young professionals. However, one should also take into account that the level of competition and workload can differ significantly across industries.