Basics of Wiring Parallel and Series
An introduction to series and parallel circuits
Series connections: When a positive (+) end from one solar panel is connected to the negative (-) end of another module it is called a series circuit or a "string." When wired in series, the voltage increases but your current will remain the same. For every connection made in series, multiply the voltage by the number of solar panels.
For example, let's say you have four solar panels that are 12VDC, 10A. When you wire all four of them in series, just multiply the voltage of one solar panel for the number of solar panels in the string. In this case, this will be a total of 48VDC.
Keep in mind that connections in series do not change the amperage. The amps of one solar panel = the amps of all four solar panels connected in series.
Parallel connections: When positives(+) are connected with positives(+) and negatives(-) with negatives(-), this is called a parallel circuit. When wired in parallel, the current (amperage) will increase with each panel.
In this case, if you were to wire the same four 10A, 12 VDC solar panels in parallel, they'd have a current of 40 amps. The voltage wouldn't have increased, so it would still be 12VDC.
One last note- always talk with an electrician before attempting any sort DIY solar project and stay in compliance with any laws, fire codes, etc. that are specific to your area. Any questions?