A delegation that abstains takes no side. It is present, it is taking part, and it has chosen to vote neither in favour nor against.
An abstention is not the same as being absent. An absent delegation has no vote at all. An abstaining delegation has a vote and has used it.
Abstaining is a real position. A delegation usually abstains when its country's policy does not let it support the text and does not let it oppose the text either.
Abstentions do not count either way. A resolution passes when the number in favour is greater than the number against. Abstentions are not added to either side, and they do not raise the number of votes needed to pass.
The chair still records how many there were. The number is part of the result and is announced with it.
Only a delegate recorded as present at the roll call may abstain.
A delegate recorded as present and voting may vote in favour or against. They cannot abstain. That is what the answer means, and the delegate chose it at the roll call. See Present and voting.
A delegate recorded absent cannot vote at all.
In MEDIMUN, roll calls are taken in MediBook and they set who can vote and how. See Committee roll calls.
There are two cases.
On an amendment of the first degree. Delegates vote in favour or against. There is no abstention on an amendment, and there is no division of the house on an amendment either. See Amendment of the first degree.
After a motion to divide the house has passed. Dividing the house removes abstentions for that vote. Every delegation that votes must vote in favour or against. See Motion to divide the house.
Abstentions are in order on an amendment of the second degree. That surprises people, because they are not in order on a first degree amendment. Both are true. See Amendment of the second degree.
Find the gap between the votes in favour and the votes against. A motion to divide the house is only valid when the abstentions are larger in number than that gap. If the abstentions could not have changed the outcome, the motion is out of order.
Take a resolution that fails on 14 in favour and 15 against, with 6 abstentions. The gap is 1 and there are 6 abstentions, so the motion is valid. The same vote with 1 abstention would not be, and with none it would be pointless.
If you are unsure. Do the arithmetic before you rule. Take the number in favour, take the number against, and find the difference. If the abstentions are not larger than that difference, the motion is out of order and you say so to the house.
Dividing the house takes a long time. Chairs should avoid it where they can.
The chair reads out all three numbers when announcing a result. In favour, against, abstentions. The abstentions are announced even though they change nothing, because they are part of the record of what the committee did.