Common fig and Fig tree

Common fig noun - Mediterranean tree widely cultivated for its edible fruit.

Fig tree and common fig are semantically related. In some cases you can use "Fig tree" instead a noun phrase "Common fig".

Fig tree noun - Any moraceous tree of the tropical genus Ficus; produces a closed pear-shaped receptacle that becomes fleshy and edible when mature.

Common fig and fig tree are semantically related. Sometimes you can replace phrase "Common fig" with "Fig tree", this phrases are similar.