The 1040 tax form is the U.S. Individual Income Tax Return form. It is a one-page form that every American tax payer must fill out to file their personal income tax. This form should be prepared and returned to the IRS every year before the required filing date.
In a way this form is the summary of your tax situation. It is where all the totals from the other schedules and forms are reported. Many other income tax forms can and must be prepared depending on your situation and the types of incomes your receive. The 1040 form comes in multiple flavors depending on your situation, such as 1040EZ, 1040A, and 1040X.
Variations of the 1040 Form
The 1040A form is shorter than the regular 1040. It is designed for individuals with less that 100,000 USD in income and do not want to itemize their tax deductions.
The 1040EZ form is the shortest form that can be filed in place of the regular 1040. It is only for individuals under 65 with under 100,000 USD in income and with simple deductions.
Forms and Schedules
Here is a link to the official IRS 1040 PDF.