"Faking it" is musicaleese for playing a song without really knowing the arrangement. You've got the melody line and you "fake" the rest.
A fake book gives the melody line, lyrics, (if any) and the guitar chords. From this, a lead player can play melody, harmony,-if he/she knows his/her chords and scales and the accompanying player(s) can play accompaniment.
There are definite techniques to using a fake book efficiently and a lot of musicians use them only to learn songs, prefering to rely on memory for performance.
It is much cheaper to buy a good fake book for, say, $40 than to buy full arrangements at $5 a pop.
The dance band that I play in (guitar and vocals) uses two fake books on a regular basis and several more for special requests made in advance. We can read cold but prefer not to; too much chance of screw-ups.
To repeat, a fake book is a very useful tool for learning songs but you are responsible for arrangements. The Hal Leonard Publishing Co. puts out my personal favorite, the "Ultimate Fake Book" series but there are many others including the "Fiddlers Fake Book" which is very good also.

troll