Divisions and brigades are formations, not units. This means that they are composed of a number of different units of different types, all working together and supporting one another. A brigade can come in several different flavours, but in its most basic form, it will contain a few infantry battalions, an armoured regiment, and an artillery regiment. A brigade will usually contain some integral service & support units. A Canadian Mechanized Brigade Group (CMBG) contains the following units, as an example(not neccessarily a comprehensive list):
3 x Infantry Battalions (2x mechanized, 1x light)
1 x Armoured Regiment (subject to change nowadays)
1 x Artillery Regiment
1 x Combat Engineering Regiment
1 x Headquarters and Signals Squadron
1 x Field Ambulance
1 x Service Battalion
1 x Tactical Helicopter Squadron
A division is just a grouping of brigades, usually with some additional units held as division resources. We don‘t effectively have a division anymore in Canada. Further, divisions are grouped together to form a corps. Corps can be grouped together to form an army... you get the idea.