"Share capital" refers to the money or assets that investors contribute to a company in exchange for ownership shares or stocks. It represents the initial financial investment made by shareholders to start or expand a business. Full definition
You might have a big amount of share capital in your bank account when you start up, but it does not mean you have to use those funds! (entrepreneur.com)
In short, when a company gives bonus shares, it's share capital increases while its reserve fund decreases. (tradebrains.in)