10/100 isnt bad, but 10/100/1000 is better if you have a gigabit switch/router/hub.
They're just different speeds, 10megabits per second, 100 megabits per second and 1000 megabits per second (AKA gigabit).
They are different standards and back in the olden days cards that were compatible with both we're known as "10/100." But now that we have 1000mbit, its 10/100/1000.