Oddly specific ads keep popping up on my web browser.

I got a new laptop last month that I've been using to stream movies and play online games. The weird thing is, I keep seeing oddly specific ads like foreign women seeking men and I have no idea how this came up. My office mate told me it has to with algorithms but I don't really know how that works. The only persons that have used my laptop are my brother, best friend, and I. How do algorithms work and what does it have to do with the ads that show up on different sites?