When you create a new workbook the default number of worksheets is 3. It is just the automatic number created. If you don't want it to do this you can change the default number created in future.
Click on the help icon and type in "change default number of worksheets" and read the article for more information.
You will learn how to make models, shortcuts and other various excel functions that are not obvious. They are great for someone who uses excel all the time.
The same exact reasons you'd use sheets in the first place. The camo pattern is just a color/pattern choice. Nobody in a tactical environment is going to have a tactical bed which they put camoflage sheets on.
I did. Once.
Excel 2013 uses a .xlsx extension.
excel
MS Excel uses two types of data: text and numbers.
Diary-keeping, letter writing, company accounts, payroll, time-sheets...
Israel uses the same system of measuring time that the rest of the world uses.
The standard extension for Excel workbooks is xls for versions up to 2003. Excel 2007 uses xlsx as its extension for workbooks.
it is not for any one to use
Excel can be used for almost anything where putting information in table format would be useful. Excel is somewhat limited in the way it handles text so if your project requires large volumes of text, MS Word would be a better option. However, if your project involves numbers (and especially if you want to perform calculations based on those numbers) Excel is a very powerful tool because of the built in mathematical functions. Excel can also be used for many other things. I have even used it to develop floor plans for a house.
Use format painter