There are generally 2 types of damage and healing, being pressure and spike.

Pressure means "consistant". Pressure damage means that you deal an amount of damage over time, and that this damage is pretty much equally divided amongst that time. The most perfectly pressured damage is health degeneration. Pressure healing means that you consistantly heal over time, with health regeneration being the purest form of it.

Spike is kind of the opposite. Spike damage means a quick burst of large amounts of damage. Downside is that spike skills usually have long recharge times (or cost loads of energy or cause exhaustion). Spike healing is the opposite, with Infuse Health being the best known spike heal.

To illustrate the difference better:
Take a mesmer with Illusionary Weaponry. This mesmer will hit the opponent for 40 damage each time he swings his weapon. Never more, never less. This is a pressure build.

Then take a character with Grenth's Balance. If the character sacrifices health, then he can produce a 300 damage spike in 1/4th of a second. But he will only be able to repeat this after 10 seconds and under VERY specific conditions. This is a spike build.


Note that healing works best against damage of the same kind, and thus damage works best against healing of the other kind .