In Japanese, all verbs may be used in an adjectival manner by adding them prior to what should be modified by the verb.1
Example: The girl who sang is sleeping
歌った少女がねている
Info
歌った (sang) is the た form of the verb 歌う (sing) and is preceding the noun 少女 (girl). This verb is describing the noun, telling us that it is a girl who sang.
歌った少女 (girl who sang) is marked by が making it the core subject of the sentence.
ねて (sleeping) is the て form of ねる (sleep). It is preceding the sentence ending verb いる (is), meaning that it is telling us more about what the girl who sang is doing. In this case, it tells us that they are sleeping. The girl who sang is sleeping.