两 (liǎng): “two,” a common way to express the number 2 when followed by a measure word or in this kind of set phrase.
岸 (àn): “shore” or “bank” (of a sea or river). It's a geographical term.
关 (guān): “to concern,” “gate,” or “to relate to.” In this context, it's part of the word `关系`.
系 (xì): “system,” “department,” or “to connect.” When combined with `关`, it forms `关系`.
The characters combine quite literally. 两岸 (liǎng'àn) means “the two shores.” 关系 (guānxi) is the standard word for “relations” or “relationship.” Together, they form “the relationship between the two shores,” a politically neutral and geographically descriptive term for one of the world's most complex political situations.