Hi, welcome to iPhoneForums 717maree. I'm Jon.
Please take some time to peruse the IPF Rules: iPhoneForums.net Forum Rules - Please Read and Respect our Rules
The blocked contact will not directly know that you've blocked them, such as receiving a message of some sort through text saying "You have been blocked by XXX-XXX-XXXX". If the person is blocked, and they call you, after a few rings, they will be directed to your voicemail. There's no indication that tells them explicitly that they've been blocked. At least not until you tell them.