I don't know the exact details of the method used in the states but the "jest" of it is:
Instead of the "the alleged criminal appearing before a judge in person to hear the formal charges and enter a plea in person, a video hookup is set up in the jail, which is two way communication.
Say the person was "arrested" and charged with five counts, well the DA may decide to only proceed with three counts nad not proceed with the other two and those charges are read out in court.
Then the alleged criminal enters a plea. This is usually done when there is no hope in heck of bail, remand is a given(as he is in jail anyways), so the person will not have to be transported to the jail.
At arraignment in the appearance of the alleged criminal, the judge will decide if bail is warranted, with the DA stating their case for remand or the conditions of bail and the Defence stating their case for bail.
In video cases, the charges are so serious and evidence is good, or the person is in jail not only for these charges but for other outstanding charges, that all that is needed to be publically informed and entered are the charges and plea.
The person is not transported to the court, as really there is no need to do that. They will not be bailed as no terms are discussed.
The States may be different, but in Canada that is usually the case.
Say a person is charged with murder, the evidence against him is pretty good, there is no way that person is going to allowed out in the community while awaiting trial, and is in prison.
Well all that is need to be infomed of is that he is charged with first degree murder, the DA will "briefly" outline the evidence, the Defence will "put up a fuss", but in the end the person stays put behind bars until trial. So he enters a not guilty and knows that the DA is proceeding with First Degree murder. In the States it may also have something to do with distance in transportation also, I am not sure.
I hope I did not "muddy" the waters any, if so please PM me and I will clarify.