Basically, we need to understand three concepts here. Before that please read the need for the cash flow statement here
This is the core of your business. If the company you are interested in is manufacturing medicines, then their core activities like selling medicines, employee salary, purchase of raw material from suppliers, tax payment etc will come under Operating activities.
When the company is involved(past) or involve(current year) in long term assets. Acquiring and disposal of long term assets comes under investing activities. For instance, when you buy a machine/plant equipment using cash, it comes under investing activities.
Raising funds through debt or equity comes under Financing activities. It also includes repaying debts. For example, when the company issues more equities in the stock market for capital investments, it comes under Finance activities
Always remember, Operating activities Net cash flow must be positive
Financing and Investing activities can be positive or negative. For that, we need to look into the annual financial statement of the company. For instance where the investments are done,how much debts are taken at what interest rate etc.