The term "手の込んだ" is described in denshi jisho as being a "Noun or verb acting prenominally". In the context of Japanese, what does it mean for something to be acting prenominally?

The term "手の込んだ" is described in denshi jisho as being a "Noun or verb acting prenominally". 

In the context of Japanese, what does it mean for something to be acting prenominally? For example, does it mean that there's restrictions on where such a word can be used?