What is CPM in Google AdWords?

CPM stands for Cost Per 1000 Imperssions (M is roman number for 1000).
Suppose if your CPM is 10$ it meanse your ad will shown 1000 times for 10$.

If your budget is 1000$ then you ad shown 100000 times.

Total Budget = 1000$
CPM = 10$

Calculation: - Impression = (Total Budget) x (1000/CPM)

Then Impression   = (1000)x(1000/10)
= (1000)x(100)
= 100000