To recover something is to get it back. After you lose your watch, you might recover it from the wastebasket.
The re- in recover is a clue that this word has "again" as part of its meaning. We can only recover things that we had before. Often, this word applies to health. Someone who is sick needs to recover — when they're totally recovered, they're all better. If the stock market crashes, it needs to recover — this happens when the market is healthier and money is flowing again. It's good to recover, but it means something bad happened in the first place.