Hey Mumof2
The symbols refer to the data connection from your mobile phone carrier. U refers to UMTS, G refers to GPRS. The U indicates you are in an area that is covered by UMTS data (faster than GPRS). While you are roaming, or in an area not covered by UMTS, the G indicates you are connected to a network tower that can support the slower GPRS data transfer speeds.
The little right/left arrows over a smaller U/G icon indicates that you are actively connected to your mobile provider's data access point. This will usually happen when you are sending and receiving data (email for example) but in a lot of cases, the connection will stay connected even when the actual sending and receiving of data has finished.
Hope that helps, and sorry for my incoherence!