Hello Akshu,
The most important difference between the two viruses is their "direction". Let's start with the positive virus:

The term positive is describing that the viral RNA is running in the 5' to 3' direction. Functionally, this means that a positive virus has RNA material that can act as messenger RNA (mRNA); it can be directly translated by the host cell.

As for the negative virus:
Negative describes direction, but this time the viral RNA runs in the 3' to 5' direction. While this can be considered a complementary strand to its 5' to 3' partner, the RNA of a negative virus cannot directly be translated into a protein. What it can do, however, is act as a blueprint to construct a strand of messenger RNA.

How you may see this presented to you is through the terms positive/negative "sense" or "strand". Using the term strand as an example. Negative viruses have negative strands that act as a blueprint to make a positive strand. Positive viruses have positive strands.

Thank you for the question and good luck in your studying,
Chris