what means?

[shaints]

class BatteryService {
public:
    /**
    * @param[ref] _ble
    *               BLE object for the underlying controller.
    * @param[in] level
    *               8bit batterly level. Usually used to represent percentage of batterly charge remaining.
    */


BatteryService(BLE &_ble, uint8_t level = 100) :
        ble(_ble),
        batteryLevel(level),
        batteryLevelCharacteristic(GattCharacteristic::UUID_BATTERY_LEVEL_CHAR, &batteryLevel, GattCharacteristic::BLE_GATT_CHAR_PROPERTIES_NOTIFY) {

        GattCharacteristic *charTable[] = {&batteryLevelCharacteristic};
        GattService         batteryService(GattService::UUID_BATTERY_SERVICE, charTable, sizeof(charTable) / sizeof(GattCharacteristic *));

        ble.addService(batteryService);
    }

    /**
     * @brief Update the battery level with a new value. Valid values range from
     * 0..100. Anything outside this range will be ignored.
     *
     * @param newLevel
     *              update to battery level.
     */
    void updateBatteryLevel(uint8_t newLevel) {
        batteryLevel = newLevel;
        ble.gattServer().write(batteryLevelCharacteristic.getValueHandle(), &batteryLevel, 1);
    }

This code is the BatteryService.h from mbed. I don't know what it is.
from line 11 to 20(looks like creator)

Is it creator? then what means

" : " (after BatteryService(BLE &_ble, uint8_t level = 100) )

I can't understand this part.

[Torsten Robitzki]

This is the constructor and what follows the collon is the initalizer list. In this list, base classes and members are initialized. That's C++ :-)