Reclassification of Items from OCI to Profit or loss

Dear Tutor

Kindly assist in explaining how, why and when items are and not reclassified from OCI to Profit or loss. I have been unable to understand what it is that gets reclassified or not and when. And from some statements it is said that the items will never be reclassified and in another it may say that items below will be reclassified. If Im not mistaken items that may fall under the OCI are as follows:

Hedging
Foreign Exchange in Subsidiary
Actuarial Re-measurement
PPE Revaluation
Strategic equity

so what does it mean to reclassify and not to ever reclassify?