After three painful days on Wall Street, there are growing concerns that stocks will enter into a “bear market.” Here is what that is and why it matters.

Stocks have been sliding since President Donald Trump announced extensive 10% tariffs on all imports and, in some cases, higher tariffs on certain countries based on trade deficits. Nearing midday Monday, the S&P 500 was down over 1% and has shed about 10% of its total value in the past five trading days.