1. There are 4 types of cadence:
Cadences
Definition: A cadence is two chords marking the end of a phrase like musical punctuation.
There are 4 types of cadence:
Perfect
Plagal
Imperfect
Interrupted

2. Each cadence sounds slightly different depending on the chords used...
These two sound FINISHED as they end on chord 1, the TONIC.
Perfect
Plagal
V - I
IV - I
These two sound UNFINISHED as they do NOT end on chord 1, the TONIC.
Imperfect
Interrupted
I - V
V - VI

3. Perfect Plagal Imperfect Interrupted V - I IV - I I - V V - VI
How to tell the difference.
Perfect
V - I
The perfect cadence is a BOLD ENDING.
Plagal
IV - I
The plagal cadence is a SOFT ENDING.
Imperfect
I - V
The imperfect cadence sounds PLEASANT but wants to CONTINUE.
Interrupted
V - VI
The interrupted cadence sounds like it will CONTINUE but to an UNEXPECTED place.

4. Example Imperfect Perfect Interrupted Perfect Plagal G Major D - G
????
V - I
I - V
????
G - D
Interrupted
Perfect
Plagal
????
V - vii
D - E
????
V - I
D - G
????
C - G
IV - I
In G Major you are looking for the following:
Chord I = G Major (GBD)
Chord IV = C Major (CEG)
Chord V = D Major (DF#A)
Chord vi = E Minor (EGB)