Field mapping, explained
Field mapping is the step in an import where you tell the system which column in your spreadsheet corresponds to which field in the CRM. The column called Mobile No. becomes the phone field, Enquiry Date becomes the created date, and City goes into a custom field you added for it. Without mapping, data lands in the wrong place or not at all.
Most importers suggest a mapping by matching column names, which saves time but still needs checking. Watch for columns that combine two things, such as a full name that should be split, dates in different formats, phone numbers with and without country codes, and values that should match a fixed list, such as lead status or source.
Map carefully once and save the time on every later import. Clean the file before importing, run a small test import and look at the results, decide how duplicates should be handled, and keep the error file from any failed rows so they can be fixed and retried rather than lost. A careful first import sets the pattern for every one after it.