Comparing characteristics using adjectives (He is taller/shorter... than her) is different from comparing actions or things.
Have a look at the sentences:
Note that to compare adjectives (nice, big, ...), you use comparative words as follows:
more [adjective] than
|plus [adjectif] que|
|less [adjective] than||moins [adjectif] que|
|as [adjective] as||aussi [adjectif] que
The adjective needs to agree in gender and number with the noun it refers to:
Whereas in English, you will need to use a subject pronoun after than (... than I (do), you (do), he/she (does)...), in French you will once again use the stress pronoun after que (... que moi, toi, lui/elle, nous, vous, eux/elles). You will also never repeat the verb with (do/am/have) afterwards.
Alice is taller than I am.
See also other Comparative structures:
Plus... plus..., moins... moins... = the more...the more..., the less...the less... (comparisons with phrases)
Better and better, worse and worse = de mieux en mieux, de pire en pire (comparisons)
De plus en plus and de moins en moins = more and more and less and less (comparisons with adjectives, adverbs, verbs)
De plus en plus de and de moins en moins de = more and more and less and less (comparisons of nouns)
Making comparisons with nouns: plus de... que, moins de... que, autant de... que
Making comparisons with adverbs: plus... que, aussi... que, moins... que
Making comparisons with verbs: plus que, autant que, moins que
And for Superlative forms, see:
Le, la, les plus and le, la, les moins = the most and the least (superlatives of adjectives)
Meilleur, mieux, pire / plus mauvais, plus mal = better, best, worse and worst (irregular comparatives and superlatives)
Le plus and le moins = the most and the least (superlative of adverbs)
Examples and resources
Comparisons: Plus ... que (video by a green mouse)