What is rule-based reasoning?

According to this:

A particular type of reasoning which uses “if-then-else” rule statements. As mentioned above, rules are simply patterns and an inference engine searches for patterns in the rules that match patterns in the data. The “if” means “when the condition is true,” the “then” means “take action A” and the “else” means “when the condition is not true take action B.” Here is an example with the rule PROBABLE CAUSE:

IF robbery is TRUE
AND
suspect witness identification is TRUE
AND
suspect physical evidence is TRUE
AND
suspect lacks alibi is TRUE
THEN
probable cause is TRUE
ELSE
round up usual suspects