second conditional 

form

condition if + subject + past simple

result

affirmative

• subject + would (‘d) + base form - example: if it rained, i would stay indoors.

negative

• subject + wouldn't (would not) + base form - example: if she didn't have plans, she wouldn't stay home.

interrogative

• would + subject + base form? - example: would you go if they invited you?

use

• to talk about imaginary or hypothetical situations in the present or future - example: if i won the lottery, i would travel the world.
• to talk about something in the present which is impossible because it is not true - example: if pigs could fly, we would see them in the sky.
• to give advice, usually with phrases starting if i were you - example: if i were you, i would study for the exam.