Most routers can be configured do run as a wifi access point quite easily. Just google your router name + "configure as access point" to check.
I've done this myself and it works well. You just need to switch of the functions on the 2nd router you want the 1st one to handle like DNS, DHCP, etc.
Wifi extender/repeater I think is where you don't even run a cable to the 2nd access point - it just "repeats" the wifi it picks up. Easy but slower and less reliable than a cable.