A fault is a part or aspect of something that is bad or doesn't work - e.g. if I am always unkind to strangers, that's a 'fault', and if my washing machine doesn't heat water, that's a 'fault' too. A mistake is something someone does that is wrong. so if do I say 1+3 = 6, that's a mistake. As people, we make mistakes because we have faults (We are not perfect). So if we make a mistake we might say "my fault", or "my mistake".

I think You can use mistake for somthing is wrong But fault you can use it for drawback or bad dehavior

I think that using a dictionary is the best way to understand this.