A typical situation to amplify an acoustic guitar is: plug straight into the mixer of the P.A or the amp. For an acoustic guitar equipped with a good pick-up this situation will work well. What about if your pick-up is not that good, sounds a bit metallic or……………..?
Instead of plugging straight into the desk or amp you could first plug into a pre-amp. A pre-amp will let you colour your acoustic guitar sound to whatever sound you want. You may want to aim for a natural, acoustic sound, or you may want to achieve a different sound from your acoustic guitar, a sound which may work better in a setting of drums and bass. Whatever sound you want you can probably get if with the help of a pre-amp.
Acoustic guitars which do have a build-in preamp may not need any of this, but if you are not happy with your sound than look into using an outboard pre-amp.
As for what kind of pre-amp to use, there are a lot of them available: There are dedicated acoustic guitar pre-amps and there are pedals which you can use for other situations as well. I like the Tech 21 Sans Amp range, you can use them for almost anything you want to colour and amplify. Just look into what you need and experiment to see what sounds right for you.
Good luck and hope to see you soon again,