The following article covers all the details about the composition of a standard electrical outlet.
NOTES: On many outlets, you may also have push in stab-in connections on the back side of the outlet, that could be used instead of the screw connections The push in stab-in connections of the back of the outlet, may be easier to use and no bending of the wire is required, even though these stab/push-in connections are suppose to be reliable, there has been instances of problem connections when using these, and my preference is to use the screw connections. Push in stab-in connections on the back of the outlet can only be used with 14 awg wire, 12 awg wire cannot and is forbidden to be used with the push in stab-in connections.
1 wire may be connected to each of the screw connections, so that an onward cable could be connected to the second screw to continue the circuit onward. You CANNOT attached 2 wires to the same screw. You may use a pigtail arrangement...
All common wires are joined together with a wire nut, incoming, outgoing, short wire going to outlet. By common I mean the ungrounded leg [aka hot conductor] wires are joined to one wire nut.
The grounded leg (aka neutral) wires are joined together with another wirenut the equipment grounding wires are joined together by another wirenut. Quite often there is 2 grounding screws in the back of the electrical box (if metallic) and you can use these two screws on the box to join 2 equipment grounding wires together.
The metal tab (4 & 11) between 3 & 5, and 10 & 12, can be broken off which will as a result break the electrical conduction between the 2 half's of the outlet, this may be done for special purposes for such arrangements as...
a) 2 - 120 hot wires [2 hot wires using a common neutral must measure 240 volts between the two hot wires not two hot wires reading 0 volts between the two wires] using the same neutral. In this case one neutral connects to the silver color screw [the joining tab (4) would remain intact (not broken)] and 2 hot wires [from different circuits] would go on the 2 brass color screws, with the joining tab (11) broken off. This kind of arrangement is often served by a 3 wire + ground cable [possibly a black, red, white, bare wire cable] the black and the red wires would be the 2 hot wires (from 2 different circuits) and the white serving as the common neutral, and the bare being the equipment grounding wire.
b) or if the joining tab (4) between the silver screws is also removed (broken off) as well as (11) the joining tab between the brass color screws (broken off) then you can have separate circuit cables serving a separate grounded leg [aka neutral] and hot to each half of the outlet giving you two 15 amp or 20 amp circuits to one duplex receptacle increasing power at that point on the wall for heavier use of power.