You can choose not to copy anything. In that case, Copy Land simply enters the battlefield as an enchantment with an irrelevant ability. We're sure you had your reasons.

In the unusual case where the chosen permanent has in its mana cost, X is 0.

Copy Land copies exactly what was printed on the original permanent and nothing more, with the listed exception (unless that permanent is itself copying something or is a token; see below). It doesn't copy whether that permanent is tapped or untapped, whether it has any counters on it or Auras attached to it, or any non-copy effects that have changed its power, toughness, types, color, and so on.

If the chosen permanent is copying something else (for example, if the chosen permanent is another Copy Land), then your Copy Land enters the battlefield as whatever the chosen permanent copied, with the listed exception.

If the chosen permanent is a token, Copy Land copies the original characteristics of that token as stated by the effect that created the token, with the listed exception. Copy Land does not become a token.

Any enters-the-battlefield abilities of the copied permanent will trigger when Copy Land enters the battlefield. Any "as [this land] enters the battlefield" or "[this land] enters the battlefield with" abilities of the chosen permanent will also work.

If Copy Land somehow enters the battlefield at the same time as another permanent, Copy Land can't become a copy of that permanent. You may choose only a permanent that's already on the battlefield.