Gram(s) is the measure in weight. There are 1000 grams in a Kilo.
Teaspoon is the measure in volume. One teaspoon equals 5 ml.
However, water is related to this
because 5 ml. or one teaspoon of water at 5 degrees centigrade
weighs 5 grams.
Therefore 1 ml. of water at a temperature of 5 Centigrade
weighs exactly one gram.
Hope this clarifies.