Prolog, short for "Programming in Logic," is a high-level programming language associated with artificial intelligence and computational linguistics. It is a declarative language, which means that the logic of the computation is expressed without describing its control flow. Prolog is particularly well-suited for tasks that involve symbolic reasoning, pattern matching, and rule-based logical queries.

• Declarative vs. Imperative: Unlike imperative languages (e.g., C, Java) that specify how to perform tasks, Prolog focuses on what the goals are.
• Logic Programming: Prolog programs consist of a series of logical statements, and the Prolog engine deduces the answers to queries based on these statements.

• Facts: Basic assertions about the world. For example, parent(john, mary). states that John is a parent of Mary.
• Rules: Logical statements that define relationships between facts. For example, grandparent(X, Y) :- parent(X, Z), parent(Z, Y). states that X is a grandparent of Y if X is a parent of Z and Z is a parent of Y.
• Queries: Questions asked to the Prolog system to retrieve information based on the facts and rules. For example, ?- parent(john, mary). asks if John is a parent of Mary.

• Unification: The process of making two terms equal by finding a suitable substitution for variables.
• Backtracking: A search strategy used by Prolog to find all possible solutions to a query by exploring different possibilities and backtracking when a dead end is reached.

Let's look at a simple Prolog program that defines family relationships:

• Facts: We have three facts stating that John is a parent of Mary, Mary is a parent of Susan, and Mary is a parent of Tom.
• Rule: We define a rule for grandparent/2 that states X is a grandparent of Y if X is a parent of Z and Z is a parent of Y.
• Queries: We can query the Prolog system to check if John is a parent of Mary or if John is a grandparent of Susan.

To run the above example in a Prolog interpreter:

1. Load the program into the interpreter.
2. Enter the query ?- parent(john, mary). to check if John is a parent of Mary.
3. Enter the query ?- grandparent(john, susan). to check if John is a grandparent of Susan.

In this section, we introduced Prolog, a declarative programming language used for logical and symbolic reasoning. We covered the basic concepts of facts, rules, and queries, and provided a simple example to illustrate how Prolog works. Understanding these foundational concepts is crucial as we move forward to more complex topics in Prolog programming.

Next, we will cover how to install Prolog on your system to start writing and running Prolog programs.