First Order Logic in Artificial Intelligence is a technique used for knowledge representation. It is an extension of propositional logic and unlike propositional logic, it is sufficiently expressive in representing any natural language construct. First Order Logic in AI is also known as Predicate Logic or First Order Predicate Logic. It is a robust technique to represent objects as well as their relationships. Unlike propositional logic, First Order Logic in Artificial Intelligence doesn't only include facts but also different other entities as listed below.

Objects:
Objects can denote any real-world entity or any variable. E.g., A, B, colours, theories, circles etc.
Relations:
Relations represent the links between different objects. Relations can be unary(relations defined for a single term) and n-ary(relations defined for n terms). E.g., blue, round (unary); friends, siblings (binary); etc.
Functions:
Functions map their input object to the output object using their underlying relation. Eg: father_of(), mother_of() etc.

Parts of First Order Logic
First-order logic in Artificial Intelligence comprises two main components, which are as follows.

Syntax:
Syntax represents the rules to write expressions in First Order Logic in Artificial Intelligence.
Semantics:
Semantics refers to the techniques that we use to evaluate an expression of First Order Logic in AI.