These traps comprise a collection of small conductive components that arc electricity between one another, damaging any opponents who tread upon them.
Some skills have a property called Next Delay that causes mobs to be invulnerable to attack for a period after the skill is used. Shock Web is one of these skills; it triggers a 24-frame (1 second) delay. Therefore, it should not be used when other (higher) damage sources are available. For instance, it is common to see trap assassins using Shock Web in public baal runs, but due to Next Delay they may actually be reducing the damage output of the team.
Unlike most other traps, shock web is not a "minion", therefore it can be benefited from items that grant -%enemy lightning resistance or +%lightning skill damage (such as lightning facet jewels).
It can be used to PK, though the damage is usually only great enough to kill players that are much lower lvl or badly geared.