All purchases made in Locus Store are paid in LoCoins (LC). That is because some payments are so tiny that in EUR or USD they would be out of payment terms of Google Play Store or Amazon and each item would require individual in-app billing entry maintenance which would be very time-consuming and bureaucracy-frustrating. LoCoin exchange rate oscillates around 1 EUR (+ VAT for EU countries) = 100 LC.
LoCoins can be acquired as a reward for recommending Locus Map to other people - your family, friends etc. You can get up to 25 LoCoins per one successful Locus installation. Number of installations in unlimited. The first item in the price list is linked to Locus recommendation page where you can send your recommendations from via e-mail.
The Voucher is sent to a user via e-mail as a reward, a gift or in a promotion action. Voucher contains a unique code that is entered into the dialog in User profile > Use Voucher. After entering the code the LoCoin credit is charged by the given amount. The only authority to send Vouchers is Asamm Software, producer of Locus Map.
Supply of purchased LoCoins, i.e. LoCoin credit serves as your virtual wallet for all purchases in Locus Map. Not only in Locus Store but also when downloading user-defined crops of paid maps.