When playing an electro-acoustic guitar without an amp, the sound will be quieter and less resonant than when it is amplified. However, you will still be able to hear the natural sound of the guitar, and it will still be suitable for practice or playing in small, intimate settings.
If you want to get the most out of your electro-acoustic guitar, it is recommended to use an amplifier. However, if you do not have access to an amplifier, or if you simply prefer to play unamplified, you can still enjoy playing your electro-acoustic guitar without one.