It's similar to an internal, except the doc uses their finger(s) to separate the amniotic sac from your cervix/uterus without breaking your water. It helps start labor in some cases, but it's not a guarantee.
definately uncomfortable, but not horrible. I had this done with DS, and it did NOTHING. My friend who had a baby in April had it done and went into labor that night.
Re: stripped membranes?