Free VPN apps for phone. Do they actually do anything?

Do they actually make your connection on public network more secure?

I recently downloaded super VPN to my phone and it's basically running in the background after I've "connected" but I have no way of telling if it's actually doing anything. Not very tech savvy with this stuff but basically I'm trying to figure out if it's actually making my browsing more secure or is it just eating battery. From my POV, besides seeing the app running in my taskbar, nothing has changed. Was expecting maybe it would slow webpage browsing or something