「もっと」 means 'more'. You use it to indicate a greater quantity, degree, or intensity of something. It often precedes adjectives, adverbs, or verbs to express 'more [of something]' or 'further'.

数量(すうりょう)や程度(ていど)が、今(いま)よりも多(おお)い事(こと)を表(あらわ)します。