Cadences are like the punctuation marks in music. Pairing chords in a certain order can create a feeling of tension, questioning, surprise or peaceful resolution.
Watch this Short-ish Explanation of Cadences to learn more.
Click Teoria.com Cadences to listen to the samples of different types of cadences.
Perfect Authentic: V-I Sounds like the end.
Imperfect Authentic: V-I + inversion Sounds like the end...but less final than perfect.