You do not need to worry about these signs. These stand for the network and the standard by which you are currently on the network.
First, there was only the GSM network, then there were improvements of the GSM network, finally the newer and faster UMTS network, and again improvements of it. The faster UMTS network is not yet available everywhere, so, often you have to go over the older and slower GSM network even today.
About the abbreviations:
- G stands for GPRS and is the slowest standard, used is the GSM network (2G).
- E is an extension of GPRS, it is called EDGE and it is correspondingly a little faster, but still uses the old GSM network (2G).
- 3G stands for UMTS and is the successor to the GSM network and faster.
- H and H+ are standing for HSPA and HSPA+. Both use the UMTS network, where H is faster than 3G and H+ is faster than H.
- 4G stands for LTE and is the fastest.