had or has/have?

hi,i get really confused about the difference between 'had given (etc..) and has/have given (etc..). i use the two interchangeably unmindful that they are quite different from each other...hope to get some help,thanks!

One is the present perfect (e.g. "have done", "has given", etc.) and the other is the past perfect (e.g. "had done", "had given", etc.). In every day speech you'd more often use the present perfect. The past perfect can be used when you're jumping back twice in time.

For example,

"I'm hungry today because I haven't eaten breakfast." or
"I was hungry last Friday because I hadn't eaten breakfast."

"Bill said 'I have to go.' to his mother." or
"Bill said that he had to go to his mother."

"I haven't studied for the grammar exam." or
"I wish I had studied for the grammar exam."

I hope this helps.

That second example is ambiguous. It sounds like Bill had to go to his mother. This is better:

"Bill said 'I have to go.' to his mother." or
"Bill told his mother that he had to go."

But it's still not such a great example because this is not past and present perfect. I think that the following would fit the bill better.

"Greg asked me 'Have you eaten your meat?'" or
"Greg asked whether I had eaten my meat."

Here's another example. I could ask you "Why have you started two threads with the same question?" or I could ask "Why have you started this second thread when you had already started a thread with the same question?" Then you could go home and say to your friends "Jim asked me why I had started two threads with the same question." or "Jim asked me why I had started a second thread when before that I had already started a thread with the question."