In Borderlands, there is a class called the Siren. One of the Siren's skills is Spark. It says that it "increases your chance of causing Elemental Effects with Elemental Weapons by 4%." What does that mean exactly? Does it mean applying the dot, chance to proc, both, or what?
The visible description is a lie.
"The definitive SPARK thread: yes, it does help HellFires." explains all about Spark handily.
Your tech pool increases by 2% with all weapons and your active regen rate increases by 0.22 with all weapons per point of spark. At 5/5 spark, this means that your weapons now have a 10% larger tech pool, that regens at 5.1 points per second (a 27.5% increase over the base of 4.0).
Spark gives your weapons a higher pool to work with, as well as faster regen, meaning your pool takes considerably longer to deplete. Once depleted, though, just like with 0/5 spark, the gun will not proc.
Also, Spark is actually more effective with guns with higher tech levels, since pool increase is %-based.
The first sentence is the absolute minimum to know, assuming knowledge of the attributes.