Investing Cash Flow refers to the cash flow generated by the company via purchase and sale of plant, property & equipment (PP&E) or purchase & sale of subsidiaries or investments in marketable securities. For example, if a company has made any purchase of PP&E, then money moves out the company and proportional amount of assets comes in. On the contrary, if a company has sold an asset then PP&E amount will decrease and cash balance will increase.
A positive cash from investing activities balance indicates that money has flown into the company because of net sales of assets whereas a negative balance indicates that assets have been bought by the company.