A bill of review is an equitable procedure similar to proceedings in error, which is filed to obtain an examination and amendment, explanation, or reversal of a final decree. There are two types of bills of review. When the decree has been signed and enrolled it is called a bill of review. When the decree has not been signed and enrolled, it is called a bill in the nature of a bill of review, or a supplemental bill in the nature of a bill of review. A bill of review must be based upon an error of law or for some newly discovered matter of fact, relevant to the case, which could not have been reasonably discovered before.