Answer:
Protectionism is a political measure that restricts the economy of a nation from trading with other countries. Thus, it seeks to "protect" the national industry, preventing foreign goods from entering the local economy through the interposition of trade barriers, such as tariffs or prohibitions, among others.
Thus, despite trying to protect the local economy, these measures restrict competition, increasing the cost and lowering the quality of products consumed in the local market, which ends up being detrimental to members of society.
Furthermore, because they are measures taken by the government, they are very difficult to avoid and overcome, at least until a change of government occurs.