Exporting individual sheets refers to extracting exactly what the user sees on the screen at a moment in time to a flat file. That flat file might be an Excel file, CSV, or other type of delimited file.
Scenario: A Finance Manager uses CPM software to monitor the company's budget and expenses. She would like to present the content of a specific sheet in her CPM tool, but would like to format it in Excel based on the CFOs very specific requirements.
Solution: Using an export function on the page of the CPM application, the Finance Manager is able to pull this data into Excel and format it.
Ideally the product can export the file in Excel format while retaining some level of formatting on the new file. It is also helpful if any formulas on the screen at the time are converted into Excel-friendly formulas. Even some Excel-based products can't do this - they have their own formula syntax that may look like Excel, but are in fact proprietary to the vendor.
Some vendors will offer an Excel plug-in which can be used to format files and keep them live. They do have limitations and are often best left in a fixed format. This is because data refreshes can ruin the formatting.
If highly formatted reports are a focus, prioritize a system with strong formatting capabilities vs constantly returning to offline Excel to accomplish this. Beware of continuing to use Excel as a crutch after purchasing a new system.