Acas is an independent body with several roles. One of its roles is to try to get you and your employer to reach a settlement about your dispute, before you make your claim or, if you have already made your claim, before it reaches the hearing stage.
Conciliation is a process through which Acas acts as a channel through which you can speak to your employer about your dispute, so that you don’t have to speak to them or their representatives directly.
Acas acts neutrally during this process; it cannot give you, or your employer, advice about the strength or weakness of your claim, or of your employer’s defence of the claim.