Network effects refer to the phenomenon where a network or system becomes more valuable and powerful as more people or components join it. Some key examples of network effects mentioned include Facebook, where the more users join, the more valuable it is due to increased social connections and content sharing; eBay, where more buyers and sellers increase the value of items; and Amazon, where more users and reviews provide more purchasing data and recommendations. A tipping point is reached when a network grows so large that users would not consider switching to an alternative due to the greater value of the larger network.