1. The problem asks whether skew lines are lines that are not parallel but lie in parallel planes. 2. Skew lines are defined as lines that do not intersect and are not parallel. 3. Importantly, skew lines must lie in different planes that are not parallel. 4. If two lines lie in parallel planes, they are either parallel or do not intersect but are not skew. 5. Therefore, the statement "skew lines are lines that are not parallel but lie in parallel planes" is false. 6. The correct definition is: skew lines are lines that are not parallel and do not intersect, and they lie in non-parallel planes.