Can I use a "Counter Target Spell" on Enchantments?
Spells are anything that you cast from your hand and add to the stack. Lands and abilities are not spells.


  A spell is a card on the stack. As the first step of being cast (see
  rule 601, "Casting Spells"), the card becomes a spell and is moved to
  the top of the stack from the zone it was in, which is usually its
  owner's hand. (See rule 405, "Stack.") A spell remains on the stack as
  a spell until it resolves (see rule 608, "Resolving Spells and
  Abilities"), is countered (see rule 701.5), or otherwise leaves the
  stack. For more information, see section 6, "Spells, Abilities, and
  Effects."


So you can counter an enchantment as long as it is on the stack (not resolved).

Lands are not spells and are not put on the stack, so they cannot be countered. Abilities however are put on the stack, but they can only be countered by spells which say they can counter abilities.