Cash-transfer programs

What are the two types of cash-transfer (conditional and unconditional). What are the differences. When the first one started and when the second one started. Briefly give an example of one specific case or country, which one do they use and how do they decide to which one to implement. Is there a context where they only use conditional, or unconditional.
This chapter to focus on what we know about the cash-transfer and development. Definitions. (more extensive) What is a cash-transfer program? philosophy? (more extensive) Briefer: How did cash-transfer programs start? When and where did they start? What were the methodologies used? What were the selection/eligibility criteria? What was the purpose behind the programs? Conditional and unconditional.