Your credit report is split into four sections.
Identifying information
Your name, current and previous addresses, date of birth, Social Security Number (usually last four), and current and previous employers. Errors here don't directly affect your score, but they can hint at mixed files (your data combined with someone of a similar name) or identity theft.
Public records
Bankruptcies. That's nearly all of it now. Equifax, Experian, and TransUnion stopped reporting most civil judgments and tax liens in 2017-2018 because the data quality was too poor to verify under FCRA standards. A Chapter 13 bankruptcy stays for 7 years from the filing date; a Chapter 7 stays for 10.
Trade lines
This is the meat of the report and the only section that drives your score. Every credit card, auto loan, mortgage, student loan, and revolving account you've ever had - with month-by-month payment status going back at least 24 months. The columns to watch: balance, credit limit (for revolving), original delinquency date (for negative items), and current status. A "30" in a payment-history grid means you were 30 days late that month; "60" means 60 days; "120" or "CO" means charged off.
Inquiries
Hard inquiries (you applied for credit) and soft inquiries (a lender pre-screened you, or you checked your own report). Only hard inquiries affect your score, and only for 12 months - they fall off entirely after 24.
For the practical guide to checking your report and tracking it month-over-month, see our blog post on checking your credit report. For the federal source, the official site is AnnualCreditReport.com.