Agile software development methodology

Research and describe the following two topics:

Agile software development methodology

What is it?

Is it more beneficial to certain types of products or certain types companies?

What are alternative software development methodologies used today?

User Stories

What are they used for in the agile process?

Provide an example of at least one user story related to a weight app that includes functionality like current weight, Body Mass Index (BMI), average weekly weight loss, weight loss to date, etc