Term length refers to the time period the coverage is active. Coverage refers to the amount of money that will be paid out to your beneficiary as a lump sum (also referred to as the death benefit).
If you purchased a 20-year term policy with $500,000 in coverage, and premiums are paid and the policy remains active, you would be covered for that 20-year period, and your beneficiaries may receive a $500,000 lump-sum death benefit if you pass away during the term.