Congruent Triangles
●   If given two similar triangles , the ratio of two
    corresponding sides is 1, then the two triangles
    are known as congruent triangles.
●   In other words we say two triangles are
    congruent if the corresponding angles and the
    corresponding sides are equal.
    A                            X
                     C                         Z
B                          Y
Note that in ∆ABC and ∆XYZ
∟ABC = ∟XYZ, ∟BAC = ∟YXZ ∟ACB =∟XZY
Also ℓ AB = ℓ XY, ℓ BC= ℓ YZ and ℓ AC = ℓ XZ
Hence ∆ABC and ∆XYZare congruent.
Denoted by ∆ABC ≡ ∆XYZ.
CONGRUENT TRIANGLES ALWAYS
Type of
           Sides of both the Triangle        Angles of both the Triangle
Triangle
  SSS         All three sides are equal
                2 sides are equal                The included Angle
  SAS                                            is equal
  ASA          Included side is equal            Two angles are equal
                Non- included side
  AAS           are equal                        Two angles are equal
 Hyp-S     Hypotenuse and a side are equal        Right angled triangle
                 Reference
For more explanations and Diagrams you can
 refer
http://argyll.epsb.ca/jreed/math9/strand3/tri
angle_congruent.htm