The GPS Trackers will send different kinds of alerts depending on the state they might be in.
All the alerts will be shown in the phone's notification area. By expanding this area we can see the details of each of them..
You do not need to have the application running to receive the alerts. When a tracker's message is received the application will handle it and show you its information, allowing you to open the application by tapping on the notification.
There are some alerts that will trigger by themselves, such as battery low alerts. There are other alerts that must be configured and activated/deactivated by the you, such as the overspeed alert.
The alerts that need configuration will be shown on the application's menu. Not all devices are capable of giving the same alerts so, depending on the configured tracker, you may see different options there.
For the alerts to be received, you must have configured the authorized phone number that the tracker must send the alerts to, as the tracker needs to know where to send the messages when the alert conditions are met.