Subgraph isomorphism problem

In complexity theory, Subgraph-Isomorphism is a decision problem that is known to be NP-complete. The formal description of the decision problem is as follows.

Subgraph-Isomorphism(G₁, G₂)
Input: Two graphss G₁ and G₂.
Question: Is G₁ isomorphic to a subgraph of G₂?