Do I need a Wifi Repeater or an Extender?

We are sharing internet with our neighbors, splitting the bill each month. Only problem is the router is in their home, we get signal but with a weak signal strength. I wanted to try and boost the signal, so should I buy a wifi repeater or an extender?

or:We are sharing internet with our neighbors, splitting the bill each month. Only problem is the router is in their home, we get signal but with a weak signal strength. I wanted to try and boost the signal, so should I buy a wifi repeater or an extender?

or:i would get them to get a wifi extender so your signal is better it might call for a separte signal booster there has to boost the signal ask the neighbor if thats okay with them that way your not blind sided