Plasterboard and dry-lining

There is no difference. Dry lining is plasterboard that uses paper and white bonding to mask the joints. Once the nail or screw holes are filled the job is finished for paint or papering. Otherwise the plasterboard is skimmed.

In the GODs they used to put the white face outermost for dry lining and the grey face for skimming with paster. The grey face has an allowance for the use of hemp to cover the joins and to stop them cracking. These days the board is only used with the white face outermost.

If someone is listing the two as separate items then I would guess that the drylining board is taper edge plasterboard, which as the name suggests has a slight taper at each long edge - much easier to tape and fill invisibly than square edge board