Sweat is the liquid that comes out of your body when you get too hot or work hard. It's like a cooling system for your skin.
When people talk about sweat, it usually means either the physical sensation of being hot and feeling moisture on their skin, or an achievement they're proud of after working really hard at something. For example, "I was sweating so much during my run that I had to stop and grab a towel" describes someone who's physically sweaty from exercising. On the other hand, "She sweated over her exam for weeks to get good grades" means she studied very hard and worked diligently to do well on the test.
Fluid that exits the body through pores in the skin usually due to physical stress and/or high temperature for the purpose of regulating body temperature and removing certain compounds from the circulation.
