This is a typical audio socket. In the datasheet there is a schematic, but it only has description for 3 pins out of 5, what is the use of the rest of the 2 pins?. Also what does the symbol in front of each pin in the schematic mean ?
The other 2 pins are usually normally-closed connections for the pins adjacent to them; plugging in a jack moves the adjacent pins away from them, breaking their connection. They are used either as sense or to shunt audio to internal speakers when no headphones are plugged in. OTOH, the fact that they aren't given in the schematic may mean that they are only for structural support.
A circle at the end of a wire indicates an external connection point where another wire may be connected either for some utility purpose or to make it part of a larger circuit.
The pins that aren't listed in the schematic are probably not connected. They may be disconnected and only present for compatibility with other connectors in the family that use them, they may be there as mechanical supports, or they may connect to internal hardware that isn't shown in the schematic! The only thing that you can safely assume, though, is that you should leave them disconnected.
If you imagine the schematic as a mechanical drawing of the inside of the connector, the schematic may make more sense. The three pins that are shown in the schematic (pins 1, 2, and 5) are connected to the contacts for the sleeve, ring, and tip of the 3.5mm connector. For standard earphones, these respectively correspond to the ground, right channel, and left channel.