on ERAS, it will ask you two questions:
1) "do you want to transmit your USMLE transcript to the programs you applied to." Answering yes to this will give them all scores from all tests that you have taken so far.
2) "do you want to AUTOMATICALLY RETRANSMIT scores for any tests that you have not yet taken or scores that are pending at the time of submitting your ERAS app.? Answering yes to this will automatically retransmit any new scores to your programs when they become available.
Everyone clicks "yes" for question number one. This is how programs select you for interviews.
Some people will advise you to click "no" for number two for several reasons. If you have not taken Step 2 before submitting your ERAS app, then you take it and fail or do poorly, choosing not to retransmit scores will prevent progams from seeing that. This allows your Step 1 scores to "carry" your application, garnering you some interviews that you likely would not have gotten if those programs knew ahead of time that you failed Step 2. (Of course, they will find out eventually, but the hope is that you still get the interview and are thus allowed a chance to explain why you failed or let your "sparkling personality" convince them to rank you despite your scores.) Another reason some people advise against retransmission of scores, is that in previous years, scores were always transmitted electronically to schools and residency programs but were sent by snail mail to students. This allowed programs to know your scores before you did, which could be a nasty surprise if you were out of town on an interview when scores were released. This is no longer such a big deal since scores are now posted on the internet for the student to view instead of being sent through the mail.