From the observer's perspective, modelling is imitating the behaviour of a role model. From the role model's perspective, modelling is the precise demonstration of a specific behaviour that may be imitated by an observer.
Humans and many animals store information about the behaviour of others and use this to make judgements about when it is appropriate to perform certain actions. Bandura said that learning would take far too long if we only relied on learning from our own experiences. We learn by observing others and we use this information later on as a guide for how we should behave.
SLT has been criticized for ignoring the influence of biological factors on social learning. Bandura claimed that natural biological differences influenced our learning potential, he thought that learning itself was determined by the environment.
However, recent research suggests that observational learning, may be the result of mirror neurones which allow us to empathise with and imitate other people.
The evidence on which SLT is based was gathered through lab studies.
Lab studies are often criticised for their contrived (deliberately created instead of naturally occurring) nature where participants may respond to demand characteristics.
E.g. it has been suggested that in the 'Bobo doll' experiment, because the main purpose of the doll is to strike it, the children were simply behaving in a way that they thought was expected.