There are many research methods every company or an individual have his/her own way of researching.

Definition-

Formal Research methods- Formal research method is defined as when the person search data from databases and libraries. This is getting the information from the primary sources such as surveys , conducting experiments, interviews etc.

Informal Research methods- Informal research methods are the methods in which the person is getting information from a secondary source. In this the individual seeks information from files like business files or this can also  be defined as conducting an informal survey.