How this number is used is if the cash per share is lower than the current stock price, then it may be an indication that current stock price may drop, but if the cash per share is higher, this could be a potential investing opportunity that signals value. Value investing is looking to get a stock many people are passing up because of various reasons, but if you dig under the hood, the engine is running just fine and the company is going through a rough patch.
Of course you have to look at other data points in fundamental investing as this may just be a good starting point. Cash per share can also be used a comparison tool across many different companies within the same industry.
The more cash a company has on hand the better because first, they are able to pay their debts back quickly if they have any. Secondly, this means they can implement a stock buy back program because if you are a current or potential investor, this means the value of stock should rise due to supply and demand.
Now you have to test this and insure it fits your current investing and evaluation style, especially if you are a technical trader as this is fundamental data. Cash is the lifeblood of a company and needs to be monitored closely, otherwise the company and you the investor could be in pinch.
With all of that being said, research the data point and find out how you can fine-tune it for your own use. Read articles and join an investing and trading group because they can help you if you have any questions. If you end up not using it, you will still have the knowledge to take with further in your financial career. Be sure not to rely to heavily on any one area because you want to paint yourself a well round picture and not be limited to one aspect. Again, you want a higher cash per share as this indicates that the stock may have more room to run to the upside.