It will give you some clues on the composition of the products based on the % of the materials that decomposes (weight loss) at certain temperature when your sample is heated at a certain rate (usually 10 to 20C per minute). During the analysis, the dimension and form the material is placed will influence the results (cut into smaller pieces, one sample in power form while the other in a cube form and etc).
If the composition of the two product is similar, it will give raise to a similar Thermogram.
I would recommend you to refer to this book:
Principles and Applications of Thermal Analysis by Paul Gabbott, Published by Backwell Publishing in 2008.