Methodology is a system of practices and procedures that a teacher uses to teach. It will be based on beliefs about the nature of language, and how it is learnt (known as 'Approach').
Grammar Translation, the Audiolingual Method and the Direct Method are clear methodologies, with associated practices and procedures, and are each based on different interpretations of the nature of language and language learning.
In the classroom
Many teachers base their lessons on a mixture of methods and approaches to meet the different needs of learners and the different aims of lessons or courses. Factors in deciding how to teach include the age and experience of learners, lesson and course objectives, expectations and resources.