Standard symbols for circuit diagrams are as follows:
Every cell has a positive and negative terminal. The polarity of a cell refers to the physical alignment of the cells in respect to their terminals (i.e. the direction they are facing). The voltage provided by cells connected in series is the sum of the voltages of each cell, having regard to their polarity. So, if two 1.5V cells are in a circuit but facing opposite ways, there is no potential difference and no voltage.
When two components are in series, the current through each component is the same
When two components are in parallel, the voltage across each component is the same as that of the supply:
and the total current taken from the supply is the sum of the currents through the branches: