How are percents used and what do they mean

They're used to measure or divide things¿

Percents are just parts of an whole. Percentages are an important part of our everyday lives. Percentage is a very handy way of writing fractions. Percentages can be compared more easily than fractions.Some example are:Shops advertise discounts on products.  These discounts are percentages.
"Up to 50% off marked prices"Financial institutions quote interest charged to the client on loans, or interest paid for money invested, as a percentage.

"Housing Loans-4.95% p.a. for the first 12 months"

Interest paid may be as Simple Interest or Compound Interest.Companies describe their success or failure as an increase or decrease in profit levels.

"C-Company profit down by 15% for the last financial year"A salesperson may be given a commission as payment for selling goods.  The commission can be a percentage of the sales made.
"Position Vacant:  20% commission on all sales to the successful applicant." Articles such as antiques or jewellery may increase in value as time goes by-appreciation. Items such as equipment and machinery usually decrease in value-depreciation