MEDITE is a powerful text comparison software that is the result of a collaboration between literary and AI scholars. It is based on string alignment techniques. The main difficulty comes from the necessity to detect displacements, which precludes the use of classical string alignment algorithms. This paper aims at introducing to the MEDITE tool. It is divided into six parts. The first describes the algorithmic difficulties of large string alignment in the context of textual genetics, because of the need to detect displacements. The second part shows the way in which the MEDITE algorithm overcomes those difficulties. The third compares the efficiency of different string alignment algorithms including MEDITE. The fourth presents the MEDITE interface, which facilitates browsing into text variants. The fifth explains what textual genetic is and how MEDITE can be useful in this field. The sixth explicates how it has been used for the edition of text variants. Lastly, the paper briefly concludes by providing details on the MEDITE software availability, on its future evolutions and on the perspectives it opens.