What are the model structures associated with enzyme action?

There are two different models theorized by scientists in order to explain the performance of enzymes that you need to know about. The first is known as the 'Lock and Key hypothesis' where in the enzyme is able to bind to a substrate (a molecule that is to be modified by the enzyme) due to the complementary shapes of both the enzyme's active site and the substrate. This model demonstrates enzyme specificity- how certain enzymes only bind to complementary substrates. You can remember this by referring back to the name of the model and how likewise only a specific key will fit into it's corresponding lock.
The second model is the 'Induced Fit' model. It is different to the 'Lock and Key' as it contradicts the supposed rigid structure of the enzyme and suggests that once the substrate, which would still have a somewhat complementary (but not exact) shape to the enzyme, has latched onto the active site, the enzyme moulds around the molecule to 'induce' a tighter fit- such as with a glove around a hand. Both theories however lead to the formation of an enzyme-substrate complex, allowing the desired molecule to be formed.