Why are there two sets of lines between the two oxygen atoms and the carbon atom?

The two sets of lines between the two oxygen atoms and the carbon atom represent double bonds. In a molecule like carbon dioxide (CO₂), each oxygen atom forms a double bond with the carbon atom, consisting of two pairs of shared electrons. This arrangement allows for a stable electron configuration, fulfilling the octet rule for each atom involved. The double bonds contribute to the linear shape of the molecule and its overall chemical properties.