A French phrasebook, for example may list a phrase like
Nous cherchons...
nu shershõ...
We're looking for...
in a section about describing the purpose of one's travels. In the entry above, the first line is standard French orthography, which any Frenchman could read, if your pronunciation attempt happened to come out incomprehensible. The second line is some pronunciation guide designed to be helpful, for you, the learner. And the third line is an English approximation of the meaning of the French phrase, also for you, the learner.
Descriptions like this, whether simply presented in a list or in some kind of table, make up a sizable portion of most phrase books. Notably absent is any kind of grammatical analysis (nor an expectation that the user of the phrasebook already has this knowledge).
Now, if all we want to do is say some French words to get by, the phrasebook approach cuts down to the bare essentials. You don't have to care about linguistic details in order to use a whole lot of French. In this way, phrasebooks can be very efficient in delivering usable, functional pieces of a language in a compact and easy to digest format.
Use it or lose it
Becoming familiar with some phrases, and not pounding one's head over the endless fount of details languages offer allows an enthusiastic student to quickly get to
using a target language. For one with the goal of speaking or writing in a language, the most valuable resources may very well be those that help you use that target language.
I have many times been a nerd and sought out comprehensive, detailed, and/or theoretically motivated accounts of languages to make sure I can get a "complete" understanding. An aspiring polyglot's bookshelf certainly has room for theoretical grammars, large dictionaries, and the whole gamut of language study materials. But as for actually getting to use a language, these resources have at times encouraged me to dive into them rather than go out into the world and actually use the target languages I've studied.
Separating theory and practical approach may be hard for the bookish, but this is perhaps what we ultimately do when we do finally end up learning.
The adage "use it or lose it" is usually used in the context of highlighting the necessity of continuing to use (and practice) skills you want to maintain. This phrase too can be used to evaluate what resources are, in practice, most valuable to us. Alas, those little phrasebooks, which essentially do away with linguistic analysis, have in recent months got much more use from me than the many more theoretically motivated volumes I have purchased.