An "opportunity" is a chance to do something great. For example, if you get called for an interview for a job that you really want, that is "an opportunity". Other examples of things that are considered "opportunities" are:

• getting accepted to a good university
• getting onto a sport team
• being promoted to a leadership position in your company

The word "opportunity" is used in the phrase "get the opportunity to (do something)":

How often do you get the opportunity to move to another country?