Full load and Rated Values of a Single phase transformer
In general, rated values are the values for which the transformer is designed and can be expected to perform as expected over the expected lifetime when operated continuously.

For the primary voltage, the transformer will overheat if operated continuously with a voltage that exceeds the rated value. It can tolerate 5% or 10% above rated, but the lifetime will be reduced somewhat. At some level of voltage, the transformer will fail quickly. If the primary voltage is below rated, the secondary voltage will be below rated, but otherwise, there is no problem for the transformer. The term "full-load" does not really apply to the primary voltage.

For the secondary, the full-load voltage voltage is applied to the load when the rated or full-load current is drawn. At less than rated current, there is less internal voltage drop in the transformer, so the voltage will be a little higher.

Exceeding the rated secondary current for very long will cause the transformer to overheat. For both the primary and secondary, full-load and rated current mean the same thing.