Maybe a couple more examples will make it clear.

echo hello
echo hello > garbage.txt
echo hello > /dev/tty
echo hello > /dev/null

The first one will display hello for you to see, and the second one will send the word hello into a file. I think that you got that much.

The third one is explicitly doing for the shell did automatically. /dev/tty is not your ordinary file, it is a "special file". Instead of being stored in a file on disk, a special little program called a driver is going to get that "hello" string. The tty driver will figure out how to make the characters appear on your screen. And then it will tell the OS, ok...that "hello" string went to the device.

The fourth one is also going to a special file and again a driver will get the string "hello". But this driver is just going to tell the OS, ok...that "hello" string went to the device. But there is no device and the null driver did not try to do anything. It just tosses the characters away.

You can read from /dev/tty. And the driver will wait for you to type something and read those characters and send them on.

You can read from /dev/null too, but the driver will always claim that there is no data.