The ranges of chest and head overlap, it's called the passaggio. Now chest and head sound quite different. Within this passaggio range you can sing notes in chest (deep, resonant, bassy) or head (thinner, lighter) or a mix in-between. In fact it's possible to smoothly change the production of the note from chesty to heady and back. Skilled singers who can use mixed voice know how to gradually reduce the chest part and increase the head part as they travel up this range (and vice versa), to smoothly join the two types of voice together and make them seem to be 'one voice'.
At your stage, you should concentrate on lowering your head voice range and increasing your chest voice range until they overlap, then you'll understand how the same note can feel and sound different in each range. Your teacher can help you do this.