The term protectionism refers to the theory, practice, laws, or policies of a government that are designed to protect domestic businesses from foreign competition, unfair or concerning business practices or foreign business and/or governments.
Examples of government protectionism would be tax cuts, subsidies, and incentives for domestic businesses; and quotas and tariffs for foreign businesses; etc.
Protectionism is sometimes criticized. Basic measures to protect a nation from things that may have a negative impact on your nation are not usually criticized, unless it is for political purposes. Criticism tends to come when substantial and potentially risky measures are taken that may or may not be in the best interests of the nation.
Country "A" decides to try to cheat and provides subsidies to its domestic automotive industry in an effort to push country "B"'s businesses out of the automotive market. Country "B" responds by placing a protective tariff on imported automobiles from country "A" in an attempt to level the playing field and to protect country "B"'s automotive industry from unfair and aggressive practices by country "B"'s businesses and government.