when you make 100$ in your Google AdSense account. If you had not hold you payment and had selected that send me my payment monthly. Then at the last day of the month for e.g. 30 or 31 date your payment over the 100$ will be calculated and will send you a Cheque. You will get that cheque at the last of the other month.
The Shape of google AdSense cheque is as below.
Inside the Google AdSense cheque