what does it mean by “debug = require(‘debug’)(‘api:server’)”

I was reading some code of a project to learn node.js then I found this line (debug = require('debug')('api:server')) which is enclosed in brackets. As I’m new to programming and when I don’t know something I just search it on the web, but I couldn’t find an answer for this one. If you are going to tell me to search on the web more aggressively then please tell me HOW too.