What is the difference between automatic and manual payment in Google Adwords?

I am going to create Google Adword campaign for my client? Which mode should I choose for payment option.what is difference between automatic and Manual payment?

A quick glance at the AdWords help pages would have given you the answer to this question. See for example:

As for which one you should choose, the above articles explain the pros and cons. Just pick whichever method suits you best.

Mike