1) What is Misrepresentation?
It is a doctrine meant to prevent unfairness when people maliciously induce others into a bad contract, or by bad conduct and carelessness do such a misrepresentation, causing injustice. Its remedies have the aim of reversing unjust enrichment.

2) Types of Misrepresentation
(i) Fraudulent Misrepresentation
This can happen when someone sells you a building with a faulty roof, and deliberately omits to tell you about such structural failure. Or if the malicious soul sells you a car with an engine he ripped out and replaced with a cheap knockoff.
If by sheer lack of diligence, the person didn't take care to find out if what he said was true. Like if someone sold you a laptop without checking if the warranty was valid, and told you it was. That would be negligent misrepresentation.
(iii) Innocent Misrepresentation
A likely possibility could be that there was an honest mistake on the vendors part. Here everyone was just unlucky. The best you can get away is a full refund.

3) How is it to be proven?
So long as there was a false statement of fact made to the person who intends to sue, and that very false statement led the person to enter into the deal, a case can be made out.

A statement of fact does not have to be mere positive words. A nod or a wink can sometimes suffice. Attempts to obscure words into half truths or to distort matters will also fall into this umbrella.

4) What solutions are available?
Generally, the most common one is rescission, whereby the plaintiff and the defendant returns all the privileges they enjoyed in order to shed the obligations they were bound to. For a simple retail case, it can be as easy as refunding a person for the purchase item.

The more complicated the contract gets, the harder it is to have a full rescission. Sometimes damages in lieu can be awarded. In that case, money is just paid.

There is also, full damages, in which the person sued is accountable for his entire misrepresentations, and has to fork out an amount that the court feels is right to award the person suing.

Perhaps you've heard about it in the course of clicking around the internet. Well, it might be useful for you or it might not. It depends...
What it is, is an act provided by legislation for certain common law territories. You would need to check if this applies to you. If it does, it can make your life much easier if you ever need recourse to this doctrine.