What is meant by data type?

Answer 1

a particular kind of data item, as defined by the values it can take, the programming language used, or the operations that can be performed on it. Example integer, float, boolean, string, character

Answer 2

In the computers the data is represented in specific ways.
Primitive (value) types (data on the stack):
bits length 8 16 32 64
numeric types byte short int long
float double

Reference (real) type (data on the heap), where
the stack holds the reference (the address) to the real data in the heap:
Classes, Interfaces, Objects, Arrays, Strings...