An ELT Glossary : Concession and contrast
Concession describes a relationship of "unexpectedness" between two or more propositions ("ideas") in the discourse. In some way, one of the ideas is a "surprising" or "illogical" continuation with reference to the other(s). For example :
He's terribly unpunctual, rarely does any work, and is really inefficient. However, they've decided to promote him.
Although it was pouring with rain, we decided to go for a long walk.
Markers of the concession relationship may be :
Prepositions - despite, in spite of
Conjunctions - but, although, though, even though
Adverbials - However, Nevertheless, Nonetheless, All the same, Regardless
Concession should not be confused with contrast - where the propositions are "opposite" in some way, but where there is no suggestion of resulting "illogicality" or "unexpectedness". The two facts are separate :
My house has two bedrooms whereas John's has three.
I can't read Anne's handwriting, but Joanne's is clearer.
Markers of contrast may be :
Conjunctions - but, while, whereas
Adverbials - However, In contrast, On the other hand, Yet