What is gram atomic mass?

Hint: It is numerically the same to the atomic mass of an element. It has a different unit.

Complete step-by-step answer:
Gram atomic mass of an element can be defined as the mass of one mole of atoms of a particular element. It is numerically equivalent to the value of the element’s atomic mass unit but has its unit in grams.
For example, the mass of one atom of carbon is $12\upsilon $ or twelve atomic mass units. The gram atomic mass of carbon would be $12g$. The numerical value of the gram atomic mass unit is also equal to the molar mass of that element. The molar mass of carbon is $12g/mol$.
All the three mentioned above have the same numerical value but denote different concepts.
- The atomic mass unit is the mass of an atom which is derived by relating it to the mass of twelfth part of a carbon atom.
- Molar mass represents the mass of $6.022\times {{10}^{23}}$ number of atoms that are present in one mole of any substance. The number mentioned in the previous sentence is called Avogadro's number after the name of its discoverer.
- Gram atomic mass actually represents the amount of atoms of a particular element whose mass in grams will be equal to its atomic mass unit. As you can see, it is only a number and therefore does not have any units like the other two.

Note: The three of them mentioned above are numerically the same but that does not mean they can be used interchangeably. In many questions this is used to confuse students. Caution must be taken to fundamentally understand the three and then solve problems based on them.