First things first: guitars come with nylon and metal strings, nylon is thicker and looks like plastic. And these are two different types of guitars.
You cannot use metal strings on a guitar with nylon strings, and vice versa. This is due to the design: the tension of nylon strings is much lower, and if you put metal strings on such a guitar, it can simply turn around.
Accordingly, you can determine which guitar is in front of you by the strings.
A classic six-string guitar is one with nylon strings. Derived from a 15th century Spanish guitar. On its basis, all modern varieties later arose. It is usually played with fingers. These guitars are used to play classical, flamenco, and bossa nova.
Classics is taught in music schools. Nylon strings are softer and thicker than metal strings, making it more comfortable for a beginner to play. The neck of such guitars is wider – it will be easier to pluck the strings due to the large distance between them.
At the same time, it is more difficult to play on such a guitar and master chords with barre – this is when the index finger simultaneously pinch all the strings. And in general, the sound when playing with a strike will be duller compared to metal strings.
A pop guitar is one with metal strings. When people say “acoustic guitar,” this is what they most often mean. In the following text, I will also call the pop guitar acoustic. Appeared at the beginning of the 20th century. It is larger and heavier than the classic one. The body is additionally reinforced with stiffening ribs.
Metal strings are more sonorous, but it will be more difficult for weak fingers to get used to. This instrument is often played in rock, pop, jazz, blues, and country. You can produce sound with your fingernails or a pick.
The neck of an acoustic guitar is thinner than that of a classical guitar and is more rounded at the back – this allows you to pinch the top strings with your thumb. The deflection of the neck can be adjusted: there is a special nut on the anchor.
An electro-acoustic guitar is distinguished by the presence of a pickup or piezo transducer – a device that removes vibrations of the strings and allows you to connect the guitar to audio equipment directly, without a microphone. This is convenient during live performances, when the musician can move freely around the stage.