How is electricity brought to the transistors?
Electrictiy is brought by wires as usual. But electricity involves 2
kinds of characteristics: voltage (in Volts: V) and current (in
Amperes: A).  Transitors and other similar devices come in various
types. The basic idea is that there are three connectors. A reference
connector (ground), and two others. One correspond to a control
circuit and the other to a controlled circuit. The transistor can have
a high or low resistance to current produced by some source, thus
controlling the flow of electricity and the voltage between the ground
and the controlled circuit connector. The state high or low resistance
is fixed by a small current (bipolar transistor) or by a voltage
(triode vacuum tube, field-effect transistor) between the control
connector and the ground.

The ground connector is called the emitter, source or cathode, for
respectively the bipolar transistor, field-effect transistor and
triode. The controlling connector is the base, gate, or grid, and the
controlled connector is the collector, drain or anode.

The idea is that the controlling circuit uses little energy to
transmit a logical signal to a circuit that can carry much more
energy (the product of voltage and intensity). This can regenerate a
distorted signal, and also make it powerful enough to be sent to
several other circuits, or actuate other devices. With appropriate
circuitry it makes for the various logical gates.

The simplest device to understand may the triode, though it is not a
transistor, strictly speaking, but its vacuum tube ancestor. There is a voltage
between cathode and anode, and by heating the cathode, the (negatively charged)
electrons are freed and can be attacted by the anode that has a
positive charge. However, there is the grid in between: if the grid
has a positive voltage, it will atract the electrons even more, and
they will speed through it with enough momentum to go through (most of
them) and reach the anode. But if the grid is charged negatively, it
will create an obstacle that electrons cross with difficulty and
little current will atually go through.  The working of the
field-effect transistor (FET) has some similarity to that, but I am no specialist.