Vectors have two defining qualities. Length & direction. We can use vectors to describe almost anything. For example if I were to kick a soccer ball; the length of the arrow would show the magnitude (the distance I kicked it or how hard) and the direction in which I kicked it. We can also use it to describe natural phenomena too such as wind. Wind has a strength/speed (magnitude) and a direction.
So if we think about a simple example of wind direction, we might get a vector like the below:
As an example, we might say that if the wind is blowing at 6MPH in a direction of -2 and I kick a football at a particular speed and direction, where will the football end up?
To find out, we do vector addition. The blue line shows the football kick and the red line shows the wind direction & speed. As a result of the wind, the actual football vector outcome will be the green line; the ball will go less distance & in a different direction entirely.
We can visualise this a little bit better. If we move the blue line (as vectors DO NOT have to start from zero) to the end of the red line, we see that the line brings us to the end of the green line. Validating that our green line is correct. We can use Pythagoras theorem to find out the length of the green side.