A "conflict of interest" is a situation in which someone might have a reason to make a decision that's not good for the group that they work for. Here are some examples of "conflicts of interest":

• An employee of your company also has a part-time job at a competitor's company.
• A politician awards a big contract to a company that she used to be the CEO of.
• A teacher's own child is one of the students in her class.

You use the phrase "conflict of interest" like this:

I think that there's a conflict of interest here that we need to discuss.

If you have a conflict of interest, that might get in the way of you making the best decision for the company.