Every grammar $G=(V,T,R,S)$ with no restrictions whatsoever besides the restrictions given^{1} in the definition of a grammar is a type-0, or phrase-structure grammar. Formal languages generated by type-0 grammars are called recursively enumerable.^{2}
Explanations: 1
A grammar has only finitely many rules, and every premise of a rule contains at least one variable. ↩
We will see later (when we will be talking about automata) that such languages are recognized/accepted by Turing Machines, therefore, they are also called Turing-acceptable or Turing-recognizable. ↩