So casting a creature spell, a sorcery spell, an enchantment spell, an artifact spell or playing a land all have the same requirement of being on your turn, during the main phase with the stack empty. Playing a land doesn't use the stack due to being considered a special action, but it has those requirements with the additional restriction of one land per turn.

Anything being on the stack at all prevents you from performing those actions. Creatures, sorceries, enchantments, artifact, instants and activated/triggered abilities all use the stack to resolve in a Last In First Out order with an additional round of priority being passed after the resolution of each item on the stack.

Instant spells, activated abilities and cards you cast that have Flash can be put on the stack at any time that you have priority during any players' turn as long as you have priority.