define "<iostream>" please !!!!!

Answer 1

Input/output stream
<iostream> is the header that defines the standard stream objects of input and output data.

Answer 2

I am not sure if you rely on Quora answers ,but the first few comments are really good for a thorough understanding of what it is

https://www.quora.com/What-does-include-iostream-h-mean-in-C

Answer 3

input/output stream