In the subject of Propositional logic, it is acknowledged that how statements are represented using Propositional logic. Here statements are limited to only factual representation. 

PL fails in representation of complex statements or natural language. As the logic got the limited expressive power. Therefore, additional logic is needed to back up the power of PL such as First Order Logic. 

Know the specifications of FOL in the following points:

• First-Order Logic is the knowledge representation used in artificial intelligence. It extends the power of Propositional logic. 
• It represents the natural language statements more precisely.  
• It is also known as Predicate logic or First-order predicate logic. It is considered to be a powerful language system that develops information more easily and expressively. 
• Unlike Propositional logic, it works on the assumption that the world is without facts but there are certain assumptions which it follows like:
• Objects: A, B, theories, practicals, colours, numbers, things, etc. 
• Relations: It can be unary relation such as: red, round, is adjacent, or n-any relation such as the sister of, brother of, has colour, comes between
• Function: Father of, best friend, third inning of, end of, ......

Being a natural language it consists of two parts:

Syntax and semantics

Given below are the basic elements of FOL

Constant : 1, 2, A, John, Mumbai, cat,...

Variables : x, y, z, a, b,...

Predicates : Brother, Father, >,...

Function : sqrt, LeftLegOf, ....

Connectives : ∧, ∨, ¬, ⇒, ⇔

Equality : ==

Quantifier : ∀, ∃

Read more: answers.mindstick.com