সমান্তরাল তল

As you know, two lines that do not intersect are called parallel lines. Similarly, two planes that do not intersect are called parallel planes. If you are familiar with vector notation, the two planes are parallel iff $\left|\hat{\mathbf{n}}_1 \cdot \hat{\mathbf{n}}_2\right| = 1$ or $\hat{\mathbf{n}}_1 \times \hat{\mathbf{n}}_2 = \mathbf{0}$.

As you know, parallel lines are lines that never intersect. It's the same principle with parallel planes. Parallel planes are planes that never intersect. Got it?