Plasterboard is a perfectly good substrate for tiling and most modern bathrooms and kitchens are tiled onto it. There are three things to get right.
Tile onto the board, not onto a skim
This surprises people, but a plastered finish is the wrong surface for tiles.
Finish plaster is a thin, relatively weak decorative coat. Bonding heavy tiles to it means the plaster becomes the weak link, and it can pull away from the board under load. Tiling directly onto the paper face of the plasterboard gives a stronger assembly.
So if you are having a room replastered and then tiled, tell the plasterer which areas are being tiled. They will leave those areas as bare board rather than skimming them. Doing this the other way round means either skimming and then tiling onto a compromised surface, or paying for a skim that has to be removed.
Prime the board first with a suitable primer. Plasterboard paper is absorbent and will pull water out of the adhesive too quickly otherwise, which weakens the bond.
Respect the weight limit
Plasterboard has a maximum weight of tiling it can carry, set out in the relevant British Standard, and it is lower than for a sand and cement render.
In practice this matters when you choose tiles. Ceramic tiles are light. Porcelain is heavier. Natural stone is heavier still, and large-format tiles in either material can take you past what standard plasterboard will hold.
Ask your tiler to check the total weight per square metre, including adhesive, against the board specification and the fixing centres of the studs behind it. Where the weight is marginal, the answer is usually to overboard with a tile backer board, which carries considerably more.
Board thickness and how it is fixed both matter. Thin board on widely spaced studs flexes, and tiles do not tolerate flex.
Wet areas need more than standard board
Standard plasterboard is not suitable for showers or any area subject to regular direct wetting. It absorbs water and degrades.
The options are moisture-resistant plasterboard, usually green-faced, or a tile backer board, which is a cement or foam-based board designed for wet conditions and which also carries more weight.
Neither is waterproof on its own. Tiles and grout are not a waterproof layer either: grout is porous and water passes through it. A shower enclosure needs a tanking system, a liquid or membrane waterproofing applied over the board before tiling, sealed at corners and junctions.
This is the single most common shortcut in bathroom work and the most expensive to put right. Water getting behind tiles into a timber floor structure in a Victorian terrace causes rot in joists that is not discovered until the ceiling below stains.
Ask explicitly whether tanking is included in your quote. It frequently is not.
Movement and joints
Leave a small gap at internal corners and at the junction between wall and floor, filled with a flexible sealant rather than grout. Buildings move, and rigid grout in those junctions cracks.
New extensions and new stud walls move more in the first year. Where a stud wall is being tiled, make sure it is properly fixed and does not flex when pushed. No adhesive compensates for a wall that moves.