What is the difference between written and wrote?

Gramatic difference and the correct way is "I've written", never "I've wrote.."

When writing "written" uses a helper (such as have or has).

"I wrote" is past tense. "I have written" is present perfect tense. "I had written" is past perfect tense, and is for special occasions. I hope you aren't writing "I written that" or "I've wrote that".