Ops are people that are able to Moderate the channel. Basically they can weed out the bad people that can find their way into the channel. Ops are also there to help you. If you are having a problem with the channel or a specific person in the channel, talk to one of the ops.
Some channels are more moderated than others.
Depending on the channel, ops have different capabilities. Most of the time, they are able to kick and ban a specific person. If you try to connect and find out that you have been K-Lined, you haven't been banned, it's just your whole ISP was banned because someone from your ISP got themselves in some real trouble with starchat causing starchat to ban your entire ISP for a period of time.