From Diablo Wiki
Status Effects are debuffs that are inflicted through varying means. A status effect can come from a critical hit from an elemental type of damage, as part of a skill (or a runed skill), and perhaps even from procs that may be present on certain item modifiers. Diablo III is a much more tactical game than its predecessors, and status effects will play a more prominent role.
 Elemental Critical Strikes
In Diablo III, critical strikes that come from elemental damage, whether it is a spell or a weapon enchant, inflict status effects. Below is a list of status effects that are inflicted through crits:
- Fire: Fire crits create a damage over time (DoT) effect on the target. This is presumably a percentage of the initial damage inflicted.
- Cold: Cold damage crits freeze the target, making them unable to move or attack for the duration.
- Lightning: Lightning damage crits stun the target, making them unable to act.
- Arcane: Arcane damage crits silence the target, making them unable to cast spells.
- Poison: Poison damage crits do not currently have a known effect.
- Holy: Holy damage crits do not currently have a known effect, if they will at all.
 Types of Status Effects
There are quite a few types of status effects in Diablo III, but currently few are known. Some overlap in function but have critical differences.
- Confusion : Confusion disorients the target, making them unable to tell friend from foe.
- Fire DoT: A fire damage over time is a critical effect from a fire-based attack, and will cause damage over time. A target with a fire DoT is easy to see, as it will literally be on fire.
- Freeze: Frozen targets cannot move or attack during the duration of the stun. A frozen target is highly visible by the fact that they'll be covered in sheeted ice.
- Stun : Stunned targets cannot take any sort of action, including movement and attack, in the duration. It uses the similar "orbiting stars" icon from Diablo II to signal to the player when a target is stunned.
- Blind: Blind targets are unable to see their enemies, and will only attack when provoked.
- Silence: A silenced target is unable to cast spells.
- Slow: A slowed target moves or attacks at a slower speed than usual. This can be inflicted by many spells, including Slow Time and Entangling Shot.
- Fear: A feared target will run in terror until the effect breaks.
The differences between some of the status effects may seem minimal, but the importance of them may also be amplified by something such as a trait. For instance, stun and freeze seem to have the same function, but if the Wizard has a trait that increases damage to frozen targets, then freeze would be a much more salient choice over a stun effect. There may also be a difference between similar status effects in terms of duration of the effect itself.
While there are no synergies in Diablo III in the same vein as we saw in Diablo II, features such as traits and attributes will play an active role in transforming the way the game is played, and how we interact with our skills.
 Status Effects in PVP
The current plan is to have all of the status effects carry over to PVP, but perhaps with down-played durations. For an example, if a Barbarian stunned you with Ground Stomp, and it normally stunned for ten seconds in PVE, it may only stun you for three seconds in a pvp arena. There are currently no specific numbers for these differences.