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 or converter. 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.