The easiest way to show you its history is with a guitar history timeline.

An easy history overview in one picture.
As you search for a "guitar history timeline" on the Net you get pages with a lot of text. I always think 'graphic' when someone says timeline.
With text you get more details but a picture like the one below presents a clear and easy overview.

The textual guitar history timeline
Of course it's possible you don't like my timeline graphic above. What can I say, I am an amateur!
What follows is a textual interpretation of the timeline picture. No long story but just dates and some quick facts. Here we go.

5000 years
Guitar like instruments have been around for at least 5000 years.

1400 BC
The Hittites played a four stringed guitar shaped instrument. The Romans adjusted a Greek guitar and called it Cithara.

By 1200 AD
Two types existed. The Moorish, with several soundholes and the Latin that looked like the modern guitar.

1400's
The Vihuela appears. A big guitar with double the strings as they used to have. Was very popular for about 200 years.

1600's
The Vihuela loses its popularity. Its to hard to tune and play. The guitar evolves to a more classical guitar like shape.

1800's
Improvements like fan struts and tuning pegs appear.

1850's
Antonio Torres Jurado joins the stage. His adjustments made the guitar the classical guitar as we know it. This guy is known as the guitar Stradivari.