After any of those transformations (turn, flip or slide), the shape still has the same size, area, angles and line lengths.

Examples

These shapes are all Congruent:

Rotated

Reflected and Moved

Reflected and Rotated

Congruent or Similar?

The two shapes need to be the same size to be congruent. (If you need to resize one shape to make it the same as the other, the shapes are called Similar)

If you ...

Then the shapes are ...

... only Rotate, Reflect and/or Translate

Congruent

... need to Resize

Similar

Congruent? Why such a funny word that basically means "equal"? Probably because they would only be "equal" if laid on top of each other. Anyway it comes from Latin congruere, "to agree". So the shapes "agree"