Aktie
... German for => share
Share here means that you have bought part of a company on paper. That part of the company is your share. It entitles you to have a say in how the company is run. It also entitles you to get some of the profit the company makes. You can buy and sell shares at the stock market. As shares go up and down in their prices all the time some people can make nice profits by dealing in shares.