Section 1572 defines actual fraud for the purposes of consent to a contract. It consists of any of five acts, committed by a party to the contract or with that party's connivance, with intent to deceive another party or to induce them to enter into the contract.
The five are worth reading individually, because they are not all the same wrong. First, the suggestion as a fact of that which is not true, by one who does not believe it to be true — the plain lie. Second, the positive assertion, in a manner not warranted by the information of the person making it, of that which is not true, though they believe it to be true — the confident assurance given without any basis, which catches the seller who says "the roof is fine" having never checked. Third, the suppression of that which is true by one having knowledge or belief of the fact — concealment, which is where undisclosed defects live. Fourth, a promise made without any intention of performing it. Fifth, any other act fitted to deceive, a residual category that stops the list being read as exhaustive.
The intent requirement runs across all five: intent to deceive, or to induce entry into the contract. What the section does not contain is the rest of a fraud claim — reliance, causation and damage come from elsewhere, and the measure of damages where the fraud concerned the purchase or sale of property is the out-of-pocket rule in § 3343. Sections 1709 and 1710 state the parallel tort of deceit, which is not confined to parties to a contract. Fraud is also a ground of rescission under § 1689(b)(1), so a defrauded party may have a choice between unwinding the contract and claiming damages. Which of those is available on your facts is a question for a lawyer.