If some ISP / Dedicated Server provider is pointing this, then Correct! One is your port capability and other one is the switch speed where you are connected. That really doesn't mean, you can take 100 Mbps as there will more users on that same switch, though your speed should be burstable upto 100 Mbit.
Also, remember 100 Megabits per second is 12.5 Megabytes per second. A lot of (false) companies boast they have "100 MB/s", which is completely different - 800 Mbit/s.