A gat-tukda has the same chaal as that of a gat and ends with the tihai of a tukda. There is a difference between a tukda and a gat-tukda. While a tukda normally is tied to one laya, a gat-tukda may also incorporate various complex phrase segments set to different layas. A gat-tukda, or "toda," oftentimes carries a variety of laya, powerful and heavy bols (characteristic of gat), and arrives on the sum with a tihai (characteristic of tukda).
Definition of gat: Click Here
Definition of tukda: Click Here