The Remote ID is the server address and the Local ID is the vpn username.
For example, if you wish to connect to server eu-fr.321inter.net
Then the Remote ID will be also eu-fr.321inter.net, and the Local ID will be same as your username.
Take a look at this settings window in IOS:
Of course your username you have to replace by your real username and put in your VPN password.
Server list : https://greatvpn.app/clientarea/index.php?rp=/knowledgebase/1/Our-DC-Locations.html
IKEv2 is also known as Internet Key Exchange version 2. It is an advanced VPN protocol that provides a balance between security and speed. It is an ideal protocol for mobile devices.