Whenever a teacher talks in terms of “placing” the tone, that teacher is talking about a result that is sought. The result the teacher is seeking may be what that teacher perceives to be the sound you should make. It may be based on another singer (whom the teacher has heard) who has an entirely different voice from yours. Your natural singing voice is closely related to your speaking voice. When you stray very far from that, you risk strain or even injury to your voice.
If you want a different sound, that sound should be your own best sound, not the sound of someone else. This will be achieved by conscientiously doing exercises to help with the coordination and strength of your voice and with getting vowel sounds to work for you instead of against you.
You cannot “open your throat,” by the way. You can open your mouth, you can open your vocal cords, you can raise your soft palate, and you can move your tongue. Too much of any of these manipulations will result in some sounds that you may not want to share with others. Take a look at an anatomy drawing of the pharynx and larynx and you will see what moves and what does not.
The phrase “everybody knows that” can be a dangerous one because it implies an absolute and universal “truth”. It is advisable to discover the source of our information.
This brings me to the next point, which is, how committed are you, to the improvement of your voice?
