constructors, copy-constructors and destructors info

Hi there! Let's start with saying that I do understand Danish, so it's not obligatory to answer in English..!-)

I would like to know a little bit about constructors, destructors and copy constructors. I'm learning from this tutorial (If I remember correctly, it's "Sam's Teach Yourself C++ In 21 Days) - and it uses these constructors, and I understand them (almost) thoroughly. It's just this one thing I'm just eager to know, how you can know when to put braces and when not to:

class SomeClass // No braces
{
public:
  SomeClass();
  SomeClass(const SomeClass &);
  ~SomeClass();
}

class SomeClass // With braces
{
public:
  SomeClass() {};
  SomeClass(const SomeClass &) {};
  ~SomeClass() {};
}

Can someone give me an answer on this and help me to understand this..? Something tells me, it's not that important, but I would really like to know what I'm doing! ;-)