Targūm is an aramaic word, then also entered into the post-Biblical Hebrew, which means “translation” and with which we designate some versions of the Bible in the aramaic judaic language.
Targums (in Aramaic: תרגום “interpretation, translation, version”) were originally those spoken translations of the Bible (Tanakh) that a professional translator (מְתוּרגְמָן mǝturgǝmān) would give in the common language of the listeners when it was not Hebrew. This had become necessary towards the end of the first century B.C., since the common language was Aramaic and Hebrew was used for little more than school and worship. The translator often expanded his translation with paraphrases, explanations and examples, so it became a kind of sermon.
Today, the common meaning of “targum” is a written Aramaic translation of the Bible.
As translations, targumims largely reflect the midrashic interpretation of Tanakh from the moment they were written and are known to favor allegorical readings over anthropomorphisms (Maimonides, for example, often notes this in the Guide of the Perplexed). This is true both for those targums that are quite literal and for those that contain many midrashic expansions.
Targumim are used today as sources in critical editions of the Bible (Biblia Hebraica Stuttgartensia refers to them with the abbreviation 𝔗).