Mein Hund ist schneller als dein Hund.
English: My dog is faster than your dog.
In German, adjectives and adverbs can be compared by changing their forms. This is called 'Steigerung' and has three degrees: positive (basic), comparative, and superlative.
Use these forms to compare things, people, or actions. The comparative is used to show that something has more of a quality than something else. The superlative is used to show the highest degree of a quality.
Mein Hund ist schneller als dein Hund.
English: My dog is faster than your dog.
Sie singt am schönsten.
English: She sings the most beautifully.
Das ist das größte Haus in der Stadt.
English: That is the biggest house in the city.
Er arbeitet fleißiger als ich.
English: He works more diligently than I do.