Here’s an explanation of commonly used trigger terms and information about what makes a good trigger. Triggers are important because they are the ultimate interface between the shooter and the gun.
All two-stage triggers have take-up, and so do some single-stage triggers. Take up describes the initial movement of a trigger before it releases the sear. Take-up on a single-stage trigger is generally very light, and for most shooters it’s undesirable. A very good single-stage trigger has no take-up.
Regardless of the trigger you have, consistency is important.
Pull weight is the amount of pressure on the trigger required to release the sear. Shooters and hunters argue about ideal pull weight. We’re talking feel, so opinions vary. A good place to start is with a pull weight no more than half the weight of the rifle. A good trigger will be adjustable for pull weight, and if your trigger has no take-up, creep and minimal over-travel, you'll generally not be able to see a difference on target with pull weights between 2.5-4.5 pounds.
Creep describes the movement of a trigger after take-up but prior to sear release. Creep is common in factory triggers and the reason many hunters opt for an aftermarket trigger, such as a Timney Trigger. Creep can be managed and worked through from a solid rest, but it very negatively impacts off-hand shooting.
Some shooters just trash their factory trigger and buy a Timney drop-in trigger to solve their trigger woes.
Over-travel relates to the movement of the trigger after the sear has been released. Few triggers have no over-travel, but a good trigger will have very little. Believe it or not, the movement of your finger on the trigger after the sear has been released can move the rifle before the bullet leaves the barrel. This is because the lock time—the time from sear release until primer ignition—allows that movement to occur. A heavy pull-weight will exaggerate the effects of over-travel.
Consistency was mentioned earlier and is probably the most important aspect of any trigger. Building a good relationship with an inconsistent trigger is impossible.
Trigger movement must happen, and when it happens consistently you will shoot better.
The last aspect of a trigger is safety. Some safeties block the trigger, some block the sear and others retard the firing pin and block the trigger. Improperly adjusted they all can fail. This means whether you have a factory or a Timney trigger, don't decide you are a gunsmith and start tweaking your trigger in ways not recommended by the manufacturer. You might create an unsafe situation.
Many manufacturers have gone to a passive—lever type—safety to allow for better triggers in their guns.