I love this unit a-lot (super fun)
So Congruent/Congruence is, For example If you have two triangles on a coordinates grid with the same coordinates than that would mean they're congruent. Shortened down would be
Same shape same coordinates same dimension same size (same everything)
Transformations would be Rotating a shape clockwise(CW)...right) or counterclockwise(CC Left)
Or Dilation which is making the shape smaller or bigger based on a scale factor.
Or reflection
How you would perform Reflection is reflect the shape over either the X-axis
Or the Y-axis
How you would perform a Translation would be to literally move the shape right left up or down.
How you would perform a Dilation(scaling) would be to pick a scale factor and either decrease or increase the size of the shape according to the scale factor number
How you would perform a Rotation would be to pick a point of rotation (P.O.R) and then pick your measure º such as 90º clockwise and rotate accordingly.
Hope it helps :)