Facts and opinions are frequently used interchangeably, yet the phrases have vastly different meanings. The validity of a statement determines whether it is a fact or an opinion.
A fact is a piece of information that can be proved to be true.    
       1. Your heart pumps blood through your body.
       2. The leaves of growing plants are usually green.
An opinion is one’s feelings or thoughts about somebody/something
       1. She looks sad.
      2. The movie was boring.
Difference between fact and opinion:
The fact is described as the statement that can be verified or proved to be true. Opinion is an expression of judgment or belief about something.
Fact relies on observation or research.Opinion is based on assumption.
The fact is an objective.Opinion is a subjective statement.
Facts explain what actually happened. Unlike an opinion, that represents a perception about something.
Facts are real information and so it cannot be challenged or debated.If we talk about opinions, they can be debated.
Some of the facts and opinions from the lesson "A Birthday Letter are:
1. On your birthday you have been in the habit of receiving presents and good wishes - Fact
2. I have liked my talks with you - Opinion
3. The best way to find what is wrong and right is by discussing - Fact
4. A letter can hardly take the place of a talk - Opinion
5. For the desire to hide anything means that you are afraid - Fact