We American citizens have several different 1040 forms and instructions sets.
1040 SC - Schedule C - profit and loss from business - sole proprietorship.
The form 1040 deals with filing status, exemptions, income, adjusted gross income, tax and credits and other taxes, credits and earned income credit, etc. as a worksheet.
The form 1040A is similar but to use it is simpler.
1040 SB is for interest and ordinary dividends.
The 1040 ES is how to figure how to pay your estimated tax on income that is not subjected to withholding. Often a sole proprietor, for example, who is earning some money would use this form to keep ahead on the taxes that will be owed.
1040 EZ is that quite easy to fill out:
Income tax form for single and joint filers with no dependents.
1040 form SA is for itemized deductions such as taxes that have been paid, gifts to charity, interest that has been paid, medical, dental, casualty and theft and miscellaneous.
1040 X - Amended US Individual Income Tax Return.
1040 SSE - Self Employment Tax
1040 SM - Making Work Pay Credit - read the instructions