A lighter’s ignition system is responsible for the spark that ignites the butane gas or liquid fuel.

Flint is a very hard quartz that sparks when struck with steel - usually a rough/serrated wheel.  While flint lighters can be very reliable, the stone does need to be replaced as it wears down.  Flint ignition systems are most popular on liquid fuel lighters. 

Piezo ignition systems rely on crystals that release an electric spark when pressure is applied.  Piezo ignition is popular on torch and burner lighters.  Typically, these ignition systems do not have to be replaced during the life of the lighter.

Battery ignition systems require a (replaceable) battery to create an electric spark.  These type lighters can power novel features like beam sensor ignition systems which are triggered by the swipe of a finger; these are especially helpful to people with limited hand mobility.

Tobacconist Tip: Always keep the lighter's ignition system clean and free of debris.  Otherwise, the spark will not be effective.