An illegal contract, by definition, is a contract that violates the law or public policies of a jurisdiction. Illegal contracts are unenforceable, meaning that the parties cannot rely on the courts to enforce the terms of the agreement.

There are various types of illegal contracts, each with their own specific name. Here are some of the most common types of illegal contracts:

1. Contracts that require illegal acts: Contracts that require one or both parties to engage in illegal activity are illegal. These types of contracts are called illegal contracts for forbidden acts.

2. Contracts against public policy: Contracts that are deemed to be against public policy are also illegal. Examples include contracts that seek to limit an individual’s freedom of speech or religion, contracts that encourage discrimination, or contracts that attempt to undermine the workings of the justice system. These types of contracts are called contracts against public policy.

3. Contracts that violate licensing laws: Certain professions require individuals to obtain licenses before they can legally practice. Contracts that violate licensing laws, such as agreements between an unlicensed individual and a client, are illegal. These types of contracts are called contracts in violation of licensing laws.

4. Contracts that involve fraud: Contracts that are based on fraud, such as contracts where one party knowingly misrepresents information, are illegal. These types of contracts are called fraudulent contracts.

5. Contracts that involve duress: Contracts that are signed under duress, such as when one party is threatened or coerced into signing, are also illegal. These types of contracts are called contracts under duress.

In conclusion, illegal contracts are agreements that violate the law or public policies. These contracts are unenforceable, meaning that the parties cannot rely on the courts to enforce the terms of the agreement. If you are unsure whether a contract is legal or not, it is best to seek legal advice.