Mars has a thin atmosphere, the pressure is about 0.6% that of the Earth's, so you would need a pressure suit on the surface. The pressure varies by time of day/ year and altitude, although nowhere is it near Earth. In most places, it's too low to allow liquid water on the surface. Water exists only as ice or water vapor although it's possible to have very, very briny water as a liquid.
Mars used to have a thicker atmosphere. About 1/3 is frozen ( as dry ice) in the poles. Early on, billions of years ago, it had a much thicker atmosphere (there are signs of torrential floods and pooling from that time). Most of the atmosphere was lost by a combination of low surface gravity, impacts and the effects of solar radiation.
There will be a test later.