That's an astronomical term that simply means you can draw a perfectly straight line between the Sun, the earth, and Jupiter as shown below. However, there is something special about this year's opposition. Jupiter is passing through the part of its elliptical orbit that is closest to the Sun. That means it will also be closest to Earth. Compared to Earth, which zips around the sun once a year, Jupiter completes one circuit around the Sun rather slowly, once every 12 years.
Opposition takes place about once per year as the Earth speeds by the slower-moving giant planet.
To see Jupiter this week, simply go outside shortly after the sun sets and look toward the east. Jupiter, blazing at magnitude -3, will be rising above the eastern horizon. The giant planet will be visible all night long. It crosses the southern meridian at local midnight and sets in the western sky at dawn. This is a good time to look at Jupiter through a telescope.