Four types cover almost every screw in a house, a vehicle or a workshop: slotted, Phillips (PH), Pozidriv (PZ) and Torx (TX). Own those four in a couple of sizes each and you will rarely be stuck. The reason to own all four rather than force one to do another's work is that each recess is made to fit one profile. A driver that only nearly fits puts the whole load on a fraction of the intended contact area, so it cams out, rounds the recess, and turns a ten-second job into an extraction job. What follows is what each type is for, how to tell the two that look alike apart, and what actually makes a screwdriver worth keeping.
Why does using the right screwdriver matter so much?
Because a screw recess is a small, shallow feature carrying a large twisting load, and it only works when the driver fills it. Cam-out, where the driver climbs out of the recess under load, is the failure that does the damage. Every time it happens it shaves metal off the flanks of the recess, so the next attempt has even less to grip, and after three or four the head is a smooth cone. The same event chews the driver tip, which then damages the next screw it touches, and it usually deposits the tip somewhere it should not be, across a painted panel or into your hand. Size matters as much as type. A PH1 driver in a PH2 screw sits deep but contacts almost nothing, and a PH2 in a PH1 screw sits proud and rocks. Neither will drive a tight screw. Getting this right costs nothing except keeping enough sizes to hand, which is the whole argument for a set from the screwdrivers range rather than the two that came in a drawer.
The four types worth owning
Slotted, or flat
A single straight slot, and still the most common fastener in flat-pack furniture, older fittings, electrical terminals and terminal blocks. Slotted drivers are not sized by number but by blade width and thickness, and the blade should match the slot closely on both. Too narrow and it twists in the slot and chews the ends; too wide and it overhangs and marks the workpiece. A slotted driver has no self-centering at all, which is why it needs steady axial pressure and why it is the type most likely to slip.
Phillips (PH)
A cross recess with tapered flanks, marked PH1, PH2, PH3 and so on. It is self-centering, which is what made it standard for production assembly, and it is what you will find throughout woodworking, construction and most appliances. PH2 does the majority of the work in general use. The tapered flanks are also why Phillips cams out readily once the screw gets tight, so keep the driver square to the screw and push as hard as you turn.
Pozidriv (PZ)
Superficially a cross, but with four additional ribs set at 45 degrees between the main slots and near-parallel flanks rather than tapered ones. Those extra contact points let a PZ driver transmit more torque with far less tendency to cam out, which is why PZ dominates European woodwork and cabinet screws. Tell them apart at the screw head: a Pozidriv screw has four fine lines stamped at 45 degrees to the main cross, and a Phillips does not. It is worth two seconds of looking, because a PH driver in a PZ screw contacts only a sliver of each flank, and it will chew the recess out from the inside.
Torx (TX) and tamper-resistant Torx (TPX)
A six-lobed star with near-vertical walls, which is why it carries high torque with almost no cam-out and why it has spread through automotive work, electronics and anything assembled by machine. Sizes are marked TX or T with a number. The tamper-resistant version, marked TPX, adds a pin in the center of the recess, so a standard TX driver will not enter it at all and a TPX driver is bored through the middle to clear the pin. That bore leaves thinner walls behind each lobe, so a TPX bit used on plain TX fasteners is the weaker of the two and is the part that will fail. Keep them separate, and note that Torx keys and bits in the hex and TX keys range cover sizes no driver handle reaches.
What makes a screwdriver worth keeping?
Three things, none of them cosmetic. First, how the blade is anchored: a blade that runs into the handle on flared wings, with the handle molded around it, cannot twist loose or pull out under load, whereas a blade simply pressed into a plastic handle will eventually spin in it and become useless. Second, the grip. A two-component handle, with a hard core for torque and a softer outer layer for purchase, lets you apply real force without the handle turning in your palm, which is what limits most people long before the screw does. Third, the tip. Tip geometry decides how much of the recess is actually engaged, and a tip machined to the correct profile grips a tight screw that a generic one slips out of. Practical extras are worth checking too: a through-hole in the handle for a lanyard or a bar, and a blade that will take a wrench where a screw is genuinely seized. For bits rather than handles, the bits and drivers range covers the same profiles for powered use.
What else will you run into?
Hex (Allen) and square drive turn up often enough to be worth a set each; hex on machinery and furniture fittings, square on decking and North American cabinet work. Security profiles beyond TPX, such as spanner head and tri-wing, are common on public fittings and consumer electronics, and a bit set covers them more cheaply than individual drivers. One category should never be improvised: for any work near live circuits, use screwdrivers built and tested for the job. IEC 60900 is the international standard covering insulated hand tools for live working, and it is what separates a purpose-built insulated driver from an ordinary one wearing a plastic sleeve. A coating dipped on after the fact is not the same thing. Check the marking on the tool itself, and start with the insulated tools range rather than improvising.