う-Verbs include all of the verbs in Japanese that end in う sounds (including some of the verbs that end in る). These verbs are called
五段（ごだん） (Godan) ‘five-step’ verbs in Japanese, due to their conjugations using all 5 of the different sounds in the same 段（だん） (column) that their base form comes from.
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私（わたし）はパンクも聞（き）く。
I also listen to punk music.
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学生（がくせい）たちは先生（せんせい）の話（はなし）も聞（き）きます。
The students listen to the teachers also.
As we can see here, the く in 聞（き）く changes to き when conjugated to the polite form. All of the other sounds the K-column will be used with 聞（き）く, depending on the conjugation. This is the same for all of the う-Verbs.
聞（き）（か）
ない, 聞（き）（き）
たい, 聞（き）
（く）, 聞（き）
（け）る, 聞（き）
（こ）う
Here we can see the
う-Verb 聞（き）く using all of the different K-column sounds in various conjugations.
Just like with る-Verbs, the base form of the verb may be called ‘plain form’, ‘casual form’, or ‘short form’, depending on the source/book.