Everyone is welcome and encouraged to attend. The colloquium talks are aimed at a more general audience than those of the specialized seminars and even first year students can profit from them. Do not forget to check their seminar schedule at their webpage. Also, many students audit classes in physics and other departments. They run quickly.
Tea time provides the ideal space for discussing math in a relaxed atmosphere.
As Professor N. Katz puts it, tea time is what you come to grad school in Princeton for. IAS also has tea of its own, served in the hall on the first floor of the Main Building. What's more, you may choose an advisor from outside Fine. Choosing an advisor is perhaps the most important decision you will make as a grad student in Fine Hall. The idea is that you have someone to talk to about starting up in Fine Hall, studying for generals, and choosing your first year courses.