The standard household electric outlet operates with 220 Volt alternate current. As this is twice the standard voltage of the US-voltage, a normal 110-Volt appliance designed for use in the US, Canada or Mexico will produce a nice display of fireworks when plugged into a European outlet.
If you bring your electrical appliances along, you will need plug adapters (in case you have a multi-voltage model) or a voltage transformer. Transformers can be heavy and very expensive, especially if you need several. It might be less expensive and less time consuming to buy new or used German appliances.