Toffee is a confection made by caramelizing sugar or molasses (creating inverted sugar) along with butter, and occasionally flour. The mixture is heated until its temperature reaches the hard crack stage of 300 to 310 °F (149 to 154 °C). While being prepared, toffee is sometimes mixed with nuts or raisins.
The process of making toffee involves boiling the ingredients until the mix is stiff enough to be pulled into a shape which holds and has a glossy surface. The resulting mixture will typically be poured into a shallow tray and allowed to cool to form a sheet. Different mixes, processes, and (most importantly) temperatures of toffee making will result in different textures and hardnesses, from soft and often sticky to a hard brittle material.
A popular variant in the US is English toffee, which is a very buttery toffee often made with almonds. It is available in both chewy and hard versions. Heath bars are a type of candy made with an English toffee core. Although named English toffee it bears little resemblance to the wide range of confectionery known as toffee currently available in the UK.
Another variant is honeycomb toffee, which is an aerated version with bubbles introduced by adding baking soda and vinegar while mixing. These react to form carbon dioxide, which is trapped in the highly viscous mixture. In the UK and Canada, the most well known honeycomb candy is the Crunchie bar. The Australian equivalent is the Violet Crumble bar. In New Zealand, this is called hokey pokey.
A particular application of toffee is in toffee apples, which are apples on sticks which are coated with toffee. Toffee apples are similar to taffy apples and caramel apples (both names for apples which are covered in caramel).
In the UK, toffee apples, sometimes called candy apples, are coated with brittle candy similar to boiled sweets.
Toffee used in confectionery can be mixed with many different ingredients to produce a variety of flavors: rum & butter, chocolate covered, vanilla & chocolate, rum & raisin, raspberry, and honeycomb.
Read more about Toffee: Etymology