One of the most important components of determining you are who you say you are at a border crossing is your mugshot. U.S. passports require that your photo fall within certain requirements for uniformity: 2x2 inches with your head filling an inch to 1 3/8 inches of that top-to-bottom dimension, color with a plain white background, facing the camera with no laughing or other facial expressions and taken within the past six months. The State Department is also picky on details such as hats and glare from a camera flash on glasses. This is all to ensure that your most accurate representation can be checked by security personnel at applicable stops along your journey.
To comply with security rules, an official short-form birth certificate that you may have been flashing for years isn't acceptable when applying for a passport. Unless you're providing a previous passport, naturalization certificate or citizenship certificate, you have to show a long-form certified birth certificate signed by a registrar. The State Department does make allowances for situations where a birth certificate cannot be produced. These multiple pieces of "secondary evidence" can include an affidavit from someone with knowledge of your birth, early school records and baptismal certificate, among others.
When you apply for a passport, you're entering the information that will fill your personal passport file. It's not just about you, though the State Department does want to know about your current job and all the physical descriptors you'd put in a personal ad. The application also wants to know about those close to you: your parents and their birth information, as well as your most recent spouse. The passport file kept on you will contain what you revealed in your application about your travel plans as well as any reports pulled on you during the application review, such as legal or financial records. If you've ever flirted with changing your citizenship, the file will include any renunciation letter as well.
For all of the security procedures the government puts into making sure you are who you claim to be, taking that passport out on the road puts this federal ID at risk of being stolen or lost. If you're overseas when this happens, report it to a U.S. Embassy or consulate. Lost and stolen passports can also be reported over the phone or by mail. Once you've reported it, the old passport is no longer valid and cannot be activated again if it's later found. If you're afraid your new passport has been lost in the mail, wait at least 10 business days from the mailing date but no longer than 90 days to report non-receipt.
