Can anyone with personal experience of this ticket restriction enlighten me as to what it means.

I am considering purchasing a super cheapo D class BA ticket down to the Caribbean from VIE (at approx half the cost of originating in London) which seems to be fully flexible and refundable but the fare notes have the notation "Changes permitted for revalidation". Does this restrict the flexibility in some way and how does revalidation work if one travels on an eticket ?