Prime video comes with prime membership and I think you can watch online. Fire stick allows streaming on tv via wifi.
Prime membership is 120 a year but it gives you free shipping on anything handled by amazon which is a great deal if you order from amazon a lot.
Fire stick can be 14.99 to 39.99 depending on whether or not it’s on sale.
For either one you do need an amazon account.
Fire stick will allow you to download different free tv apps
and you can also get premium apps like HBO. There is also a youtube app and a browser.
Quick and dirty description. Somebody else probably can describe it better and in more detail.
You could also go to amazon.com or search engine for more details.
On the fire stick slide, I have one. Had 2, but had to return on to my TV provider when I gave up “cable” (actually, fiber, but same price and same channels). I use my fire stick for watching Sling and Pluto TV. I can switch to antenna mode for the local channels. Much cheaper than what I was paying for my cable.