All network connectable devices have a unique address for their connection method, the MAC address - this is nothing to do with Apple, it stands for Media Access Control. In the case of devices which have bothj ethernet and wifi connectability there are two addresses.
A MAC address looks like this example: B8:3E:59:C8:EB:1B (this belongs to a dead device so it's not a security risk publishing it).
Your wifi router may be set up to allow only specified MAC addresses to connect, as a security measure. This is probably located somewhere in the settings as 'Access Control'.
If this is the issue you have two choices. You can turn off access control so any device can connect (if it knows the password). Or you can find out what the MAC address of your device is and add it to the router's access control list.
Unfortunately many devices don't tell you the address until you've connected, which is a bit Alice in Wonderland, so you have to turn off access control, join the network, look at the list of connected devices and work out the MAC address from there. Responsible manufacturers include the address on the device exterior or in the packaging, but this is increasingly rare.