A mobile phone is a portable wireless technology that enables calls to be made and received by users. Although only communications could be made and received by the earliest generation of mobile phones, today's mobile phones do a lot more, accommodating web browsers, games, cameras, video players, and navigational systems. Also, although mobile phones used to be known simply as "cell phones" or cell phones, because of all the extra voice and data services they provide, today's mobile phones are more generally called mobile phones. As stated, the first cell phones were used only for making and receiving calls, and they were so bulky that it was difficult to hold them in a pocket. The primitive RFID and wireless systems were used by these phones to carry signals from a wired PSTN endpoint. Mobile phones actually belonged to the network of the Global System for Mobile Communications (GSM) were later able to send and receive text messages. As these devices evolved, features such as Multimedia Messaging Service (MMS), which allowed people to send and read images, became smaller and many more are added.