Basically, your soundcard or mixer setup is passing your input signal through to your speakers in real-time at the same time Live is processing and passing the input signal out with a delay (this is your system's latency), so two parts of your system are doing the same job, one faster than the other, hence the delayed echo. It's usually best to go with the zero-latency monitoring built-into your soundcard or from your mixer.

Go to your Live Preferences, Audio, and turn Monitor Through Live = No.