If you give this Access Point the same WiFi SSID and password as your current Netgear, then devices can potentially "roam" between them when moving from one floor to another.
This is true, but some devices are very bad at giving up a negotiated link, so you might end up with bad performance because your device is trying to not to the AP that was the closest when you brought the network up, but you then walked to the other floor. So you may (depending on your devices) need to force your WiFi to reassociate (usually disconnecting and reconnecting to WiFi does this) if you're roaming from one AP to the other frequently.
There are fancier setups where you have multiple APs and a central controller; the advantage of these systems is the controller can decide that you're talking to the "wrong" AP and force you to disassociate. I don't personally know many people who have bothered with something this complex in their home, but it's quite common if you're trying to setup WiFi for a campus.
Good reply! One detail I'd add:
This is true, but some devices are very bad at giving up a negotiated link, so you might end up with bad performance because your device is trying to not to the AP that was the closest when you brought the network up, but you then walked to the other floor. So you may (depending on your devices) need to force your WiFi to reassociate (usually disconnecting and reconnecting to WiFi does this) if you're roaming from one AP to the other frequently.
There are fancier setups where you have multiple APs and a central controller; the advantage of these systems is the controller can decide that you're talking to the "wrong" AP and force you to disassociate. I don't personally know many people who have bothered with something this complex in their home, but it's quite common if you're trying to setup WiFi for a campus.