Roku is a streaming platform. You can use it to watch Netflix, YouTube, Hulu, Disney+, etc. The actual device varies, as ‘Roku’ is just the name of the company and platform. They have streaming sticks, which are little rectangular devices that you plug into your tv’s HDMI port to make any tv a smart tv. They also have larger, non-stick shaped versions that do the same thing, just at higher quality/more features. They also have soundbars with Roku built in.