In physics, a quantity can be described by its dimensions which will be some combination of the base dimensions of mass, length, time, current, amount of substance and luminous intensity.
Working with dimensions is similar to working with units as we learn to do in AS physics but a dimensional analysis, where a formula or set of equations is tested for homogeneity, is traditionally preferred over a units analysis.
The presentation here is designed for a teacher to use with students  if you need more guidance then download the presentation and look at the notes that go with the slides.
Further consideration is given at http://www.schoolphysics.co.uk/age1619/General/text/Dimensions_/index.html and also in Gareth Kelly and Nigel Wood's excellent book 'Mathematics for A Level Physics: A Course Companion'.
