As A country with country B, two countries will benefit the country itself, but that is not a member of the free trade zone will be pushed. Called to discourage trade.
For example, country A to country B will benefit the two countries, but countries outside the EU who are not members of the FTA will be sidelined. Known as a trade barrier
As the country A with country B two countries will benefit, but the country outside of the group that is not a member of free trade will be extracted. It's called a protectionist trade.