Step 1: Understand informal organization.
Informal organizations are formed through personal relationships and mutual interests among employees. These organizations rely heavily on the goodwill and personal efforts of employees rather than formal structures.
Step 2: Evaluate the options.
- An informal organization depends on the voluntary cooperation and the 'sweet will' of employees, as there are no formal structures to enforce rules or procedures.
Step 3: Conclude.
The correct answer is informal organization.
Final Answer:
\[
\boxed{\text{Informal organisation}}
\]