10-Q - this is a company's quarterly report. As a general rule, the 10-Q is less detailed than the annual report. Companies are required to file their 10-Q within 35 days of the end of their quarter. The financial statements that are included in a quarterly report are generally unaudited.
10-K - the annual report that is filed (yearly) by a company. This is an extremely in-depth document that contains everything that you ever wanted to know about the company. Executive compensation. Audited financial statements. Organization structure. Etc. Etc.
8-K - a form that is filed by companies to inform their shareholders of "unscheduled material events that are important to shareholders". CFO leaves. SEC is launching an investigation. The company announces a new business deal. Delisting notice. Shutting down a plant. Layoffs. Bankruptcy. These are all material events that would require an 8-K to be filed. The 8-K is extremely common, and many companies will file a number of 8-K's throughout the course of a quarter.
seeking alpha: change ticker in url
https://seekingalpha.com/symbol/MSFT/financials/sec-filings
or q10k
https://q10k.com/msft
historical data on income statements, balance sheets and cash flows is available at
https://finance.yahoo.com/quote/MSFT/financials?p=MSFT