The online application opens up for about a month six months before the internship semester begins. Following the online application, you will be notified regardless of whether you move or not. If chosen to move on, a recruiting coordinator or someone similar will contact you for a phone interview with the recruiter hiring for the position. It lasts about 20 minutes and he/she asks basic interview and follow up questions on your resume. Following the phone interview, you will be notified if you move on for an in-person interview at HQ. Again, pretty basic question and follows an unstructured format. They go down your resume and asks you to expand on your experience and duties and ask probing questions to get a better understanding of how you work, how you like to be managed, and to try to gauge the breadth of your knowledge.
Since the initial contact from the recruiting coordinator, the whole process took 2.5 weeks. However, be patient because they receive literally thousands of applications! I submitted my application in November and did not hear back until February.