What is the difference between absolute and comparative advantage?

so absolute compares how many plates one produces vs the other country while comparative compares how their opportunity cost differs. Is the PPF always linear? If not, wouldn't this make the comparative advantage calculation much more difficult?

Is it possible that one country has a comparative advantage?

Is it possible that one country has a comparitive advantage in the production of some good while the other country has an absolute advantage in the production of that same good? Yes, all it requires is that the comparative advantage i.e. opportunity cost of making that good for Country A is lower than Country B, regardless of absolute figures.

What is a comparative advantage?

When a country or business has multiple resources to produce various goods and services rather than focus on just one product, it may look for a comparative advantage. Comparative advantage explains why companies, countries, or individuals benefit from trade.