The text in the dialog is an improved variant of the text given by the diff command with the -u option. You can see the differing versions in two windows, with lines arranged such that you can do a side-by-side comparison. That means, where text has been added or deleted, the respective window shows empty lines with the marker +++++ at the left hand side. Elsewhere, you can see the running number of each line in the left column.
O texto no diálogo é unha variante mellorada do que dá o comando diff coa opción - u. Pode ver as versión diferentes en dúas fiestras, coas liñas dispostas de tal xeito que poda facer unha comparación lado- por- lado. Isto significa que onde se engadise ou eliminase texto, a fiestra respectiva mostra liñas vacías co marcador +++++ á esquerda. En todos os casos, pode ver o número de liña na coluna da esquerda.