A necked down .308 case. Between the .243 and .308, the 7mm-08 is a neat little cartridge. Great for deer and with premium bullets is adequate for elk (not my first choice though). The fact that it's case length fits short actions is another plus. Some good rifles chambered for it are Browning Micro Hunters, Remington Model 7, Savage 11, 14, and 16, and Tikka T3. There are others that I am positive I missed because everyone makes a rifle in the 7-08.
Find one that you like and fits you best and you will be happy.