Your first script

Create hello.server.clpp. The .server tag means Rojo will treat the output as a Script.

#include <clpp/roblox.clh>

struct HelloServer {
    void Greet(Player player);
};

void HelloServer::Greet(Player player) {
    post("Player name: " .: player.Name);
}

void init() {
    HelloServer hello;
    Players players = GetService<Players>();

    for (Player player in players.GetPlayers()) {
        hello.Greet(player);
    }

    players.PlayerAdded~>Connect(func (Player playerEntered) {
        hello.Greet(playerEntered);
    });
}

Line by line

1. #include <clpp/roblox.clh> — IntelliSense for engine types. No Luau is emitted for this header.
2. struct HelloServer + void HelloServer::Greet — define methods with ::. Call them with . (hello.Greet(player)).
3. player.Name — property (dot).
4. "Player name: " .: player.Name — concatenation (.: → Luau ..).
5. void init() — runs at the end of Scripts and LocalScripts.
6. GetService<Players>() — typed service lookup.
7. for (Player player in players.GetPlayers()) — range-for. in is the collection.
8. players.PlayerAdded~>Connect — . reads the signal, ~> gives Connect to Janitor. Manual (no janitor) is ::Connect.
9. func (Player playerEntered) { ... } — anonymous callback. Luau closures still see outer locals. There is no C++ capture list [].

Compile:

clpp compile hello.server.clpp

You get Luau with function HelloServer:Greet, game:GetService("Players"), and an init() call at the bottom.

Next: Mental model.