1) Comparative adjectives compare one person or thing to another or to itself at a different time, often using "than". Superlative adjectives indicate something has a quality to a greater degree than others in a group.
2) Comparative and superlative adjectives can be used before or after verbs and nouns. Adverbs of degree can also modify comparatives.
3) Specific constructions like "the...the", two linked comparatives, or prepositional phrases specifying a group can also be used with comparatives and superlatives. The same rules apply to comparative and superlative adverbs.