Theorists emphasize that social institutions exist because they perform five essential tasks: replacing members; teaching new members; producing, distributing, and consuming goods and services; preserving order; and providing and maintaining a sense of purpose.

functional theorists

Explanation:

Functional theorists believe that every single members of the society have their own functions and they are dependent upon one another. For a society to be successful, Every single members of the society need to fulfill their role.

To guarantee this, society tend to create social institutions to act as the regulator and enforcer (i.e : the government)

The instituions have 5 essential task :

replacing members;

Sometimes a member will become too old to fulfill his/her role. The institutions need to replace that member with a younger one.

teaching new members;

This is achieved through education (school and universities are good example for this.) They teach people new skills that can be used to fulfill their role)

producing, distributing, and consuming goods and services;

Doing all these things will keep the economy going and gradually improve the quality of life of the citizens.

preserving order

This function is aimed to keep the members safe from threat. They need to punish the members of society who hurt other members (criminals)

providing and maintaining a sense of purpose.

They need to inform the members regarding the things that they wish to achieve in the future. This will maintain a sense of purpose among the members.

productive most commonly means: achieving or producing a significant amount or result.

explanation:

productive can also mean:

these depend on how the word productive is used. most likely productive will mean   achieving or producing a significant amount or result.