THC is the chemical that makes people feel high or stoned and it can have a very wide range of effects depending upon the individual. However, it is also known to have therapeutic properties. CBD leaves people clear headed, but it interacts with receptors throughout the body and as such, it also has many therapeutic uses. Furthermore, CBD is known to limit the effects of THC. Therefore if a strain is particularly high in THC but also has a high CBD level, then the effects of the THC will be somewhat mitigated.
A CBD-THC balanced strain may not have the same level of both, but it will produce a balanced effect. It can still have a psychoactive effect, but it will be less intense than THC-dominant strains. CBD can reduce the ability of THC to cause anxiety, the two chemicals work in synergy to produce an enjoyable experience with less potential for negative side effects.