What is the distinction in terms of variation between working capital and working capital need?

I think the answer of Mr Ibrahim is fine. 

It not only affects general management, but also the access to bank credit or the valuation of the business, for example. This is calculated as follows:

Equity capital and other resources in the long term - fixed assets

This allows you to see whether sufficient long-term funds are available to finance the production chain. Where there is a positive result that is indeed the case, whereas with a negative result it is actually the production chain that must safeguard the long-term financing.

It is therefore useful to calculate the working capital needs as well:

Current assets (excluding cash) - current liabilities (excluding financial liabilities)

The result shows the amount the business needs in order to finance its production chain, and may be both positive and negative:

• where working capital needs are positive, the commercial debts no longer cover the short-term assets (excluding the financial). In that case, a business can rely on its working capital. If this is insufficient, it will need additional financing for its operational cycle in the short term.
• where working capital needs are negative, a business can meet its short-term liabilities without any problem. Nevertheless, it is advisable to reduce working capital needs (further).

In other words, it boils down to limiting working capital needs as far as possible, thus increasing liquidity. This is crucial, especially in times of economic or financial difficulty. After all, customers tend to pay later then, while your stocks are increasing and your suppliers are imposing stricter payment terms. As a result, more and more working capital gets 'frozen' in your operating cycle, precisely when circumstances make it more difficult to attract additional financing.