The document explains the second conditional used for discussing hypothetical or imaginary situations and their consequences, such as 'if I won the lottery, I would travel around the world.' It outlines the grammatical structure, including the use of 'were' or 'was' after 'if' and how to differentiate between first and second conditionals based on the likelihood of the situation. Examples are provided to illustrate the usage of 'would,' 'could,' and the implications of real versus imaginary scenarios.