Well in Easton's Bible Dictionary

(Heb. beer), to be distinguished from a fountain (Heb. 'ain). A "beer" was a deep shaft, bored far under the rocky surface by the art of man, which contained water which percolated through the strata in its sides. Such wells were those of Jacob and Beersheba, etc. (see Gen. 21:19, 25, 30, 31; 24:11; 26:15, 18-25, 32, etc.). In the Pentateuch this word beer, so rendered, occurs twenty-five times.