The Android Emulator emulates Android devices on your computer, allowing you to test your application on a range of Android API versions and devices without having each real device.
The emulator gives the following benefits:
Flexibility: In addition to simulating a number of devices and Android API versions, the emulator includes preconfigured configurations for Android phone, tablet, Wear OS, and Android TV devices.
High fidelity: The emulator replicates almost all of the features of a genuine Android smartphone.
You may simulate incoming phone calls and text messages, select the device’s location, simulate various network speeds, simulate rotation and other hardware sensors, and access the Google Play Store, among many other features.
Speed: In some respects, testing a software on an emulator is quicker and simpler than on an actual device.
For instance, you may send data to the emulator quicker than to a USB-connected device.
When you use the Android Studio emulator into Android studio, emulator screen gets close with android studio closure itself.
In order to get the Android Studio emulator in a separate window, Go to Preferences –> Tools –> Diff & Merge –> Emulator and uncheck the ‘Launch in a tool window‘ option.
Now close and restart the android studio emulator, you would be able to access the Emulator screen into separate window than Android Studio.

Once you able to open the Android Studio emulator in a separate window, if you launch any project, it would open into separate window and would work an an independent application.
Even if Android studio is closed, emulator screen will be open separately.