One of the classic lexicons published by the Oxford University Press about a hundred years ago, this volume is commonly known as BDB. It's still one of the most useful dictionaries of Hebrew, tho' the scholar will probably use the 'Hebrew and Aramaic Lexicon of the Old Testament' by Koehler and Baumgartner (HALOT) especially as there's a inexpensive (ha-ha!!! it's v. costly, but by Brill standards it's cheap!) 2-volume Study Edition available now. But I prefer to use BDB for non-academic use, and strongly recommend it to students, as it is in Hebrew root order. This means it is a bit harder to find the word when you start learning Hebrew, but the advantage is you have most of the words related to the word you are looking for sitting together on the page, which gives you a bit more insight into the word. It also is very good on words in related languages, which can be useful to those who know them. But for the beginner, it can be quite hard to find some difficult words (you need to know your broken verbs well), so I would recommend having a copy of another old favourite, the Langenscheidt Pocket Hebrew Dictionary, as a backup in case you really can't find that word.