Biblical Hebrew, also called Classical Hebrew, is the archaic form of the Hebrew language, in which the Hebrew Bible and various Israelite inscriptions were written.
It is not spoken in its pure form today, although it is often studied by Jews, Christian theologians, linguists, and Israeli archaeologists to help them gain a deeper understanding of the Hebrew Bible and Semitic philology. Classical Hebrew is also generally taught in public schools in Israel.
Biblical Hebrew and modern Hebrew differ with respect to grammar, vocabulary, and phonology. Although Modern and Biblical Hebrew's grammatical laws often differ, Biblical Hebrew is sometimes used in Modern Hebrew literature, much as archaic and Biblical constructions are used in Modern English literature.
To see the difference let's take the following sentence: "Moses went to the mountain."
In modern Hebrew we use the same syntax as in English: "Moshe (Moses) halakh (went - past tense) La-Har (to the mountain)."
משה הלך להר
In Biblical Hebrew they used a coordinating conjunction + verb in future tense to describe an action occured in the past. The same sentence would be then like this: Wa-yelekh (and he will/shall go) Moshe (Moses) el (in direction of) Ha-har (the mountain).
וַיֵּלֶךְ מֹשֶׁה אֶל הַהָר