Before telling, I want to define "volunteership" as the activities which help people that who have been damaged from by a natural disaster.

When the   a natural disaster happens (-S), so many people are damaged and the amount extent is so large. It means that it is impossible to help the damaged people with normal emergency programs or social welfare systems. It is needed lots of people  Lots of people are needed to reconstruct collapsed buildings and supply foods or clothes for the damaged people.

These helps This help makes people be united to the community firmly and we can have loyalty to our society with the beliefs that we can get the help from others when we have difficulty.

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1) Be careful of your relative pronouns. Normally I don't see this problem from you, so I'm assuming it was a simple mistake.
Activitities which help people who are damaged.

2) Lots of people are needed
--This is the passive voice. You can Google it and find some good websites explaining it.
Basically, it's our way of putting emphasis on the object in a sentence.

3) Help is an uncountable noun. It goes under the intangible category I told you