The origin of Tanabata festival came from the legend of the ancient Chinese Dynasty so called 'kuikouden' '乞功奠' (the Chinese writing) Long time ago, there was a woman called 'Syukujo' (織女 in Chinese writing and Vega in English.) the dress making lady in the heaven. Her dress making skill was so special. However since she got the husband, called 'Kengyu' (牽牛 Chinese writing, Altail in English) she was crazy about him and never concentrated on her dress making job.This made the God of Heaven angry and he took her husband 'Kengyu' away to the other side of the galaxy. Moreover, The God made the strict rule to them. It remains that 'Syukujo' and 'Kengyu' could meet only once in a year, which is the evening of July 7th. Yhat was the origin for Tanabata Festival and it came from the legend (kikouden) '乞功奠' from ancient Chinese Dynasty. The real meaning of this legend in China is, not to be lazy and that one should work hard to bring one's skill up.
In Japan, since the Heian Era, firstly this Chinese legend had been told only among the Emperor's family. In the middle of Edo Era, this legend gradually got to be known around the ordinary citizens. As in China, the legend of 'kikouden' '乞功奠' remains to encourage people to work hard to improve their job skills.

Seven kinds of decoratoins

Fukinagashi
It's aymbolies sewing line.

The net
It's symbolises of fisherman's net.

Orizuru
To wish for ones family's long life.

The dust box
It symbolies towards not to litter the environment.

Tanzaku
A paper used to write someone's wish.

The sac bag
Do not spend too much money. Save the property.

Paper Kimono
It beaome a scapegoat of one's bad luck.