Ark is full of surprise and give you best aspect of game with fine creatures and dinosaurs that other games lacks. If you run it on your PC, the game is full of fun and addictive too that you keep on playing and can host Ark Servers before the settings are optimized.
First you have joined the server or local play then you can see Heads Up Display. It is displayed on the bottom of your screen where characters status bars display.
It shows your experience which will go up when full and level up.
It will show your weight that you fill and will be laden more. That will reduce slowly as per speed, mostly to a half. Do not carry more weight, you can have storage box on ark servers.
It shows your level of thirst when full and thirst is satisfied. As it starts reducing you will feel thirsty. So once empty you can get damaged and die eventually. Replenish your thirst for swimming in water. Also you can make water skin so that you can fill shallow water by using items. It will replenish your thirst and fill water skin for drinking later.
It shows hunger same as thirst but refills differently. When you run low you can eat meat or berries.
Stamina reduces while jumping, sprinting, fighting, sprinting, swimming etc. and hits 0 when you can walk only. If you swim it will reduce constantly until you are down. So you can run or jog to get stamina back other than waiting to run and force you to walk little bit.
Ark servers will show your health straightly. This can be refilled easily if you take lot of cooked meat and blood bags. You can lose your health anytime so hit something using your hands.