#1
Does that mean it can be played without an amp and it will sound like a acoustic guitar and then you can switch it to an elctric by plugging it in?
#2
Kinda. It's basically an acoustic with pickups installed, so you can play it unplugged or through an amp. It's not gonna sound like an electric guitar, though. Just an...amplified acoustic.
#3
An Electro-Acoustic is an acoustic with a mic inside it.

Ibanez SR506BM
Ashdown Little Giant 1000w
Peavey TVX 115+410
A big ass upright

#4
It's an acoustic guitar with a pickup and a jack that allows you to connect to an amp and amplify the sound it usually makes.
Basically it would be about the same thing as putting a mic ,connected to an amp, near your guitar.