Long ago the Mines of Phandelver were notorious for the riches, both in gold and magic. After a vast source of magical energy was uncovered it became highly sought after by Mages of all types. Greed and lust for power brought the demise of the Mines after one glorious battle where none survived and those who knew the location of the mines avoided them.
In time the location of the mines were lost. After many years adventures began to search for the mines to no avail. Hundreds failed, many of them died in the attempt. The new found interest in the mines brought a turned Phandalan, then nearest village into a boom town. Now it is bustling with commerce and adventurers seeking treasure.
Now after all this time, rumor has it that three dwarf brothers have finally found the mines and are about to reopen them. One of the brothers has gone to Neverwinter for supplies and tools.
After that, take a look at your wiki. There is some more helpful info there.