Sales reports show where leads drop off, which channels bring revenue and whether you will reach your target. This article explains each report and how the forecast is calculated.
Open Reports in the sidebar and choose the Sales tab. The section is called CRM Reports. Pick the period (the last 30, 90 or 365 days, or a custom range) and choose Export to download the current report as a CSV file.

CRM Reports with the lead-to-won funnel and step-by-step loss
The report catalog under the tabs lists every question the reports answer.
The forecast includes deals won in the period and open deals whose close date falls in the period or is empty.
Choose Save snapshot to keep a copy of today's forecast for comparison later.

The Forecast tab with quota, closed, commit, best case and pipeline per owner
The Sales overview shows the same figures in summary: open pipeline, weighted forecast and deals won or lost this period.
Reports and Forecasting are modules that your plan may or may not include. If the Forecast tab says forecasting is not included, ask your account owner.