Two truths: Conventional truth and Ultimate truth

Conventional truth

Superficial or relative truth; one's common everyday perception of phenomena and reality, with all its concepts and habits, including characteristics perceived by the senses (color, sounds, smells, tastes, texture, shapes, thoughts etc.), that which is true from a conventional or common viewpoint in which phenomena appear to exist inherently. Conventional truth is often referred as an obscured or concealed truth, implying a perception which is limited and/or partially mistaken. It is mistaken in the fact that the way phenomena are perceived and the way they ultimately exist are not the same. With that said, we can further define conventional truth as that which is true for an obscured mind. Conventional truth can be additionally divided into right and wrong conventional truths.

Ultimate truth

Absolute or final truth; the sublets truth; the ultimate and accurate perception of the true nature of phenomena and reality uncovered through analysis or perceived directly by superior beings. That which is true from an ultimate viewpoint in which the emptiness of phenomena is unmistakably perceived. Because of its unobscured and unconcealed nature, ultimate truth is posited as non-deceptive truth, meaning that the way phenomena appear to the mind and the way they truly exist are the same. With that said we can further define ultimate truth as that which is true for an unobscured mind. In other words when analyzing the ultimate nature of something, that which is found is the phenomena's lack of inherent existence. The fact that all phenomena are empty of inherent existence is the ultimate truth and ultimate reality.

Note
Although the senses of ordinary beings are invaluable to our daily lives, they are considered unreliable tools for discerning ultimate truth. This is due to the fact that there are many ways in which our senses can be deceived (mistaking a rope for a snake, mistaking a stranger for a friend etc.) But most significant is the way our senses continuously misinterpret the nature of reality. Reason gained through analysis as the most reliable tool and the only way for ordinary beings to properly apprehend ultimate truth.

Read full free e-book 
Tibetan Buddhist Essentials: A Study Guide for the 21st Century, Volume 2: The Buddha's Teachings – Tenzin Tharpa