Whether it was for a course assignment or a peer-reviewed article, at some point you were probably told that neutral and passive writing is preferred. You should write something like 'The physics of frog levitation is described', which should sound objective, stressing the subject discussed rather than the author doing the discussion. Another possibility would be to use first-person singular pronouns -- as in 'I describe the physics behind frog levitation'. Some feel that this choice overly stresses the actions taken by the author, overly glorifying herself. The third possibility is using first-person plural -- as in 'We describe the physics behind frog levitation'. This choice supposes to feel participative, as if the author and the audience are collaborating.
