Most of them aren’t even a hotspot (cell connection to wifi). Main features are:

• VPN to make it appear as if you’re in another country
• wifi sharing. Let’s you use a single WiFi connection for multiple devices. Some hotels and many airlines/cruise ships charge per device and sharing makes all your devices appear as one. Also convenient because you only need to set up the new Wi-Fi on one device (the rest are already configured to your travel router).
• acts as a repeater. Helpful if the wifi only works well on one side of the apartment you’re renting