PlayerPrefs stores simple values without manually creating a file.

Supported types:

int
float
string

Save:

PlayerPrefs.SetInt("Coins", coins);
PlayerPrefs.SetFloat("Volume", volume);
PlayerPrefs.SetString("Name", playerName);

Load:

int coins =
    PlayerPrefs.GetInt(
        "Coins",
        0
    );

Useful methods:

PlayerPrefs.HasKey(...)
PlayerPrefs.DeleteKey(...)
PlayerPrefs.DeleteAll()
PlayerPrefs.Save()

Best for settings and small values, not large save games.