can anyone explain frost to a Newbie

People sell the main exp room for around 1.5m.

But hypering 4 bosses > Oceana + mobs + heads

Frostcovered City (FCC) is an example of a 'zhenning' instance that is used to gain high amounts of experience.

Zhenning is basically teamwork killing. The cleric uses their blue bubble (reduce damage taken and aoe heals), the barb uses their high defenses to round up many mobs (in some cases 60+ at a time) then aggroes them. The DD's in the squad then kill the mobs while the barb holds aggro. When done properly you can kill large amounts of mobs in a very short time and get a ton of experience. People then augment this with their hypers on 12x.

FCC is arranged as long halls crowded with mobs ending in a gate keeper mob. So the barb pulls all the mobs to the gate keeper mob, aggros everything, the squad aoes the mobs all at once. The barb then moves straight into the next pull to the next gatekeeper. There are also 5 bosses needed along the way that give excellent experience, especially when hypered.

The reward for getting to the experience room and killing the 6th boss are "heads." This is kind of like mice bashing where head mobs appear and don't attack, but if you hit them they die and give you a large amount of exp (again, hypered). 50-80 heads spawn in 3 minutes.

People use this to level their characters in the 80-100 range since BH and quest exp becomes a very small amount. Many people drag low levels through FCC (I remember gaining levels 35-48 in one 3 minute heads run, and level 19-23 on a single boss). Others clear the FCC till the exp room and then sell the room to low levels for around 300k ea or 1.2-1.5m for the whole room. A level 90ish squad takes around an hour to clear, but a 5 aps level 100+ can solo it in around 30 minutes.

I see this is an older thread but thought I'd add a more comprehensive answer.

Shayd - Raging Tide wrote: »

Frost is the solid deposition of water vapor from saturated air. It is formed when solid surfaces are cooled to below the dew point of the adjacent air as well as below the freezing point of water. Frost crystals' size differ depending on time and water vapour available. Frost is also usually translucent in appearance. There are many types of frost, such as radiation and window frost. Frost causes economic damage when it destroys plants or hanging fruits. If a solid surface is chilled below the dew point of the surrounding air and the surface itself is colder than freezing, frost will form on the surface. Frost consists of spicules of ice which grow out from the solid surface. The size of the crystals depends on time, temperature, and the amount of water vapor available. Based on wind direction, "Frost arrows" might form.
In general, for frost to form the deposition surface must be colder than the surrounding air. For instance frost may be observed around cracks in cold wooden sidewalks when moist air escapes from the ground below. Other objects on which frost tends to form are those with low specific heat or high thermal emissivity, such as blackened metals; hence the accumulation of frost on the heads of rusty nails. The apparently erratic occurrence of frost in adjacent localities is due partly to differences of elevation, the lower areas becoming colder on calm nights. It is also affected by differences in absorptivity and specific heat of the ground which in the absence of wind greatly influences the temperature attained by the superincumbent air.
The formation of frost is an example of meteorological deposition.

You're quite welcome

Technically deposition doesn't occur because it passes through a liquid phase no matter how fast its cooled (deposition or desublimation is going directly from a gas to a solid).