Most of these stats a fairly standard for miners - but here's some general info:

As to what are shares – shares are completed units of work that have been submitted to the mining pool. The higher the difficulty a share was mined at, the more the share is worth. The mining pool automatically calibrates difficulty so your miner finds one around every 30 seconds. Higher hash rate miners can solve higher difficulty shares and consequently have higher yields.

Errors are when you miner submits a share and the pool cannot validate or redeem it. Reasons for this can be if there is a mathematic error in the share (sometimes an indicator of a hardware issue but this is rare). More commonly, errors happen when a work item that the miner was working on goes stale and is replaced by a newer work item. Bitcoin Miner is designed to submit the old share just in case it can be redeemed, but in these situations errors nothing to worry about. Generally they happen when work items change quickly such as when the pool and miner haven’t settled into a steady state and the difficulty is changing.

I have searched and I cannot find anything explaining what shares are. I think that kH/s is kilo hashes per second but I cannot find anything explaining shares, errors and difficulty. I assume that errors and difficulty are not important and I assume that shares are related to Satoshis but other than all that I cannot find explanations. Please do not say to search the internet unless you at least are sure the information is available. Please someone at least explain what shares are in the context of this program.

Some doco on the main screen would be helpful, even as mouse over tool tips.

Google is your friend my friend

What is a share?
What is difficulty?
What do Errors mean?
What does nn.n KH/s mean?