Have read lots of different terms. I have no idea how they differ from one another.
Things like, 20% stock pool for employees, and 1 million stocks, etc.
Can someone enlighten me?
The "capital stock" is the capital the company was founded with. It is divided up on individual shares. You could have found that on Wikipedia.
In day to day business speak it's common to use "shares" and "stocks" (note plural) as synonyms, i.e. they normally mean exactly the same.
The "options pool" is a number of shares which are earmarked / reserved for future employees. In other words, it's a pool of shares that will be used for share options for employees, as an incentive on top of their salary.
The key things to know about the options pool are:
In addition to the above link to Venture Hacks, you should also see their Excel spreadsheet for building a capitalization table. In general, go read lots of Venture Hacks articles, they're great.
Shares are synonymous with stock in the sense that both represent % ownership of a company/companies.
20% ownership pool for employees refers to the percentage of the company reserved for employees (assuming full dilution).