There are several characteristics that differentiate the two types of whales including their size, social structure, breathing (number of blowholes), dentition (teeth or baleen plates) and echolocation.
As a whole there are currently estimated to be around 80 known species of whale between the toothed and baleen species.
Toothed whales as you probably guessed it have teeth which they use for grabbing and eating their prey.
These type of whales have a single blowhole as compared to the two blowholes found in baleen whales.
The majority of toothed whales (with the exception of the sperm whale) are smaller than their baleen whale relatives, but are known for eating larger prey from fish, squid, octopus and crustaceans to various marine mammals depending on the species.
Due to their smaller size some species of whale stand a greater chance of being hunted and attacked by predators such as sharks.
This type of whale also tends to have a much larger and more sophisticated social structure when compared to baleen whale species.
Toothed whales make sounds using their blowholes and are not born with vocal cords.
They also have well-developed echolocation abilities that they use to locate food and find other objects in the ocean.
Male toothed whales tend to be larger than their female counter parts.
Baleen whales aka the great whales have baleen plates (which resemble the bristles of a comb) instead of teeth and filter food through their baleen plates while allowing water to pass through.
Filter feeding is a common method for baleen whales.
Filter feeding works by swimming forward with their mouth open and scooping up prey such as fish and squid which get caught and stuck in their baleen bristles while allowing water to scape.
Baleen whales typically eat small prey such as fish, krill and plankton which is partly due to having baleen plates instead of teeth, which could be used for chewing.
This group of whales is (for the most part) larger than their toothed whale relatives.
Baleen whales have two blowholes instead of one.
Female whales are typically larger than their male counter parts.
Baleen whales tend to prefer traveling in small groups known as pods or alone.
Unlike toothed whales it is believed by some biologists that baleen whales do not use echolocation, instead they communicate by creating a series of loud low-pitched sounds, and some whales such as the blue whale and humpback whale produce melodic tones which is commonly referred to as a whale song.
Note: The blue whale which (the largest of the baleen whale species) is considered the largest known mammal on this planet and can grow as large as 110 feet.