The Rules of A Scientific Methodology
As a means of testing the validity of knowledge, Popper proposed a set of "rules of scientific methodology" which he termed the "Hypothetico-Deductive Model" of science.
"Hypothetico" means "based on hypotheses" and for Popper, the research process revolves around the ability to develop and clearly state hypotheses that can be tested in some way through social research.
Deduction (or to give it its proper name, deductive logic) is a way of making authoritative statements (proofs) about what is not known by a thorough analysis of what is known. The ability to make deductive statements is a very powerful tool since it is the basis for drawing logical conclusions about specific events from general events.
In sociological terms, a model is a small-scale representation of something (such as, in this instance, a research process) that helps us to clarify the relationship between the things involved by describing the relationship between them in simplified terms. In this case, Popper's model suggests the various steps we need to follow in order to "do research" and, as such, helps us to organise the research process.
To put this in simpler terms, you will probably be familiar with fictional detectives such as Sherlock Holmes. He solved a crime by systematically investigating a case, collecting and analysing facts and, on the basis of these facts, naming the person who committed the crime. This is an example of deduction because Holmes was able to authoritatively state (or prove) something specific (the identity of a murderer, for example) that was not initially known on the basis of his general observations about things that were initially known (the facts surrounding the case).