Tesla Motors:
Tesla Motors is a company that designs, manufactures, and sells electric cars including the Tesla Roadster, Model S, and Model X. Their first car, the Tesla Roadster, was the first electric sports car made. The company was founded in 2003 by a group of engineers who wanted to design the world’s first electric cars. The Tesla Roadster came out in 2008 and four years later, Model S hit the streets. Model S is a sedan that can travel from 0 to 60 mph in 4.2 seconds and travel 265 miles per charge according to teslamotors.com. The Model X is in production now and it is supposed to arrive in 2015. They are designing it as a mix between an SUV and a minivan to accommodate different types of people and families. 
The difference between regular cars and electric cars are the superchargers. It lets Model S and Model X owners to charge their cars at locations around the world. Electric cars may be more expensive but they can travel much more miles on one charge as opposed to a regular car on a tank of gas. For example, the Roadster can travel 245 miles per charge and the Model S can travel 265 miles per charge.
Tesla Motors have also helped by lowering the dependence on petroleum-based transportation thus lowering the price of electric cars. Their goal is to make the cars more affordable to people and putting more electric cars out on the street.
Electric Cars replace the Internal Combustion Engine with an electric motor. The motor converts electricity into mechanical power and it also turns mechanical power into electricity like a generator. With the Internal Combustion Engine, only 30% of energy in gasoline is used to move the car and the rest is wasted as heat and noise. Also, torque is instantly available at an RPM (Revolutions per minute) while torque is only available after many thousand RPMs in an engine. When the car is in need of a charge, any 110-volt or 220-volt outlet can be used for charging the battery. This gives the owners freedom to charge it whenever they want or whenever they need to.
Fisker Automotive:
Fisker Automotive was founded by Henrik Fisker and Bernhard Koehler in 2007. The first premium hybrid electric car, Fisker Karma, arrived in mid-2011. The United States Bankruptcy Court for Delaware filed an order for the sale of Fisker Automotive in February of 2014. Wanxiang America Corporation is the new owner and the company was renamed, The New Fisker.
Like the Tesla vehicles, the Fisker Karma has a large battery pack, but it also has a small gasoline engine as well. The battery can also be charged at outlets in a home. They also have solar cells that can be placed on a roof of a house or garage to help recharge the battery. It has two modes-the Stealth Drive and the Sports Drive. In the Stealth Drive, it is quiet, like Tesla vehicles, and it can travel up to 50 miles per charge. It has no emissions and it can travel from 0 to 60 mph in 7.5 seconds. In the Sports Drive, it can drive up to 100 miles per gallon. It can go from 0 to 60 mph in 5.8 seconds. It releases some emissions in this mode, it is still less than a regular gasoline engine. In general, electric cars are expensive but they are a better option for the environment and does not release any emissions.
References:
http://www.teslamotors.com/about
http://thenewfisker.com
http://auto.howstuffworks.com/fuel-efficiency/hybrid-technology/fisker-karma3.htm
http://www.teslamotors.com/roadster/technology/motor