Firefighter short-hand: what does it mean?

I realized this morning as I was captioning a photograph on my morning update ("2nd alarm, Newark, NJ, heavy fire conditions in a single-story, commercial taxpayer. All hands working.") and I realized, unless you are a firefighter, you probably didn't understand what I was talking about. Using the photo at left, I will give you the short-hand description - that we would transmit over the radio - and then explain it in plain language.

Short-hand version:

W/F on a two story commercial structure with apartments above. Advancing 1.75" hand lines to the front door on the alpha side. Have the second due engine establish positive water supply. DWH. All hands working.

Plain language explanation

Crews arrived at the two story building that has a business (commercial) occupancy on the first floor and residential (apartment) occupancies on the second floor. The first engine on the scene is going to advance multiple one and three quarter inch hand lines to the front door. The officer on that engine is requesting that the next engine to arrive connect to the nearest fire hydrant (and then to the first engine) to establish a positive water supply. Based on the conditions observed on arrival, the officer suspect that it is doubtful that he will be able to hold (contain) the fire with the units currently on the scene. This indicates to the 911 center / alarm center / radio room to be prepared to dispatch multiple units ("alarms") to assist with the containment operation.