To obtain a personal travelcard, you must have a Finnish social security number. The customer information will be filed. You can order the card and buy tickets onto it online. If you don't have a Finnish social security number, you can obtain a holder-specific travelcard.
The age group set on the card changes according to your own age.If you lose your card, it can be closed and replaced with a new one.The card can be topped up with special tickets and benefits, like student and senior discounts. You can also pay some sport services (eg. public swimming pools and gym fees) with a Stored Value Ticket.
You can borrow your card, unless it contains no personal tickets or benefits. The borrower has to belong to the same (or lower) age group as you.