The thousandths place in 275,608 is the 5. Depending on the next number (which in this case is the 6) it will either round up or down. Since the next number is 6 and it's 5 or bigger, the 5 will round up. So your final answer is 276,000.
Scientific notation is a system for expressing very large or very small numbers in a compact manner. It uses the idea that such numbers can be rewritten as a simple number multiplied by 10 raised to a certain exponent, or power.
