What do WPA2 and WPA3 mean?
Answer first
They are ways of encrypting a wifi network. The newer one is better, but the older one is still fine with a long password.
Both are ways of encrypting wifi traffic, so that a neighbour or a passer-by cannot read it.
WPA2 has been in use since 2004 and is still enough with a strong password.
WPA3 is the newer one. Its most important improvement is that guessing at a weak password is harder.
The newer one only works if the router and the device both support it. Plenty of older devices do not, which is why routers offer a mixed mode.
If your settings still show WEP, that is a different matter. It has been broken and should not be used.