In the UK (and presumably all other countries) the men went to war and the women were mobilised as a workforce. Obviously pre-war women had jobs and worked, but nowhere near as many as when war came.

In the UK it was seen as everyone's duty to "do their bit" for the war effort. Anyone who shirked this "responsibility" was looked down on. I believe this was also prevalent in the USA, the women would want to "do their bit for their boys".

Women found themselves in factories making engines, building aircraft, packing explosives - pretty much anything that was used to fight was made in factories. My grandmother worked as a riveter on spitfires for example.

Other women were sent to farms to help the farmers replace the male farm hands that they had lost to the military. The women became known as the Land Girls, officially called the Womens Land Army. This was hard work, but essential to feed the country and of course the military.

One fairly small, but very brave group of ladies joined the Air Transport Auxiliary. the ATAs job was mainly to fly aircraft from the factories to their operational bases or from airfields to repair facilities and so on. Many RAF personnel were quite taken aback to see a Spitfire, Hurriane or even a big bomber - right up the to a Lancaster touch down at an airfield, taxy to a stop and see a dazzling young lady emerge!! Most of these ladies were already trained pilots, but even so, they'd fly solo, unarmed in all weathers, they pretty much navigated by landmarks - church spires, hills, roads and so on.

Within the military, the British Army had the Auxiliary Territorial Service that women served in, these were mainly support jobs - drivers, running mess halls and so on. The WAAF (Womens Auxiliary Air Force) ended up with over 180,000 women serving. Probably the most important job they did was working in the chain home stations, where the fighter squadrons who were defending the country were controlled from. Some WAAFs crewed on barrage balloons or packed parachutes for the pilots. I believe some WAAF also worked in intelligence, looking at reconnaissance photos etc. Of course there were plenty of women working at Bletchley Park, the centre of UK code breaking/cryptography. I am unsure of their status though, I assume they worked for GC&CS (Government Code & Cipher School, the forerunner to GCHQ), which would make civilians.

Of course many women were nurses. looking after injured soldiers during their recovery/rehabilitation.

So in short, women on the home front did pretty much every job you can think of, bar active service (e.g. firing a gun/flying sorties/serving on war ships). Their contributions were invaluable to the war effort.