The "T" may point to thermal ability to carry a certain average or rms current. The cooling is an important parameter in this case.
But, it may also - depending on what company's data sheet you are looking at - indicate the thyristor's transient (surge) current capability. So, unless you specify manufacturer or provide a link to the data sheet in question, it is next to impossible to say what the actual meaning of these terms are.
Keep also in mind that the conduction angle plays a role. For ms current pulses, the i[sup]2[/sup]t integral is more useful and should be used to select protection (almost always fast acting fuses in this case).
Is there a link to the actual data sheet? That would help.
Semikron says that this is a Thyristor/Diode module. There are characteristic curve families for both components. The T suffix says that data are valid for the Thyristor (SCR) part and the D suffix is for the Diode part.
The picture showing the module is misleading since it shows two Thyristors and no Diode. The text under the picture says: "The actual product may differ from image shown", which it obviously does, in this case.