If you do get spotted, there is a small chance you can run away and hide, but if multiple enemies start attacking you, it is very unlikely you will make it out of the encounter alive. So you have to be smart, because if you do take any damage, it takes a few seconds just to apply the medical kit and regain part of your health. Enemies range from various infected creatures, to normal human beings, and with each type of enemy, you need to understand the dangers they pose before attacking them recklessly.
The "clickers" for example are infected enemies that can't see, but use a form of echolocation to find out where you are by clicking. Your companions will usually recommend that you steer clear from these enemies by distracting them with a throw-able object, as they are quite difficult to kill, and will usually require you to use one of your more precious resource such as shivs or bullets. The dangerous thing about these enemies is that the only way to survive if they grab you is to use up one of your shivs, whereas with others you can get away with mashing the square button and attacking them with a melee weapon.
I honestly expected this game to be Uncharted, with a different skin, and whilst there are certain elements that are familiar, such as the stealth mechanics, there is a lot that is different. First of all, there is relatively little platforming, although this does exist in some form. Secondly, there is also a greater focus on scavenging items, and you'll find yourself looking through every nook and cranny so that you can take full advantage of the item components you can get. Thirdly, there is no way to "shoot from the hip" and you must always aim using L1, and R1 to shoot.
Ellie is a surprisingly useful companion. There are situations when a health icon will appear above her head, but for the most part she tends to hide away from enemies with you. If she does get into an encounter with them, she can jump on an enemy and distract them long enough to let you attack them. This is unlike companions that we've seen in other games such as Resident Evil 5, where the companion was more of a hindrance than any real help, and would of course glitch out often.
You can create items such as health packs and weapons at any time during the game, all you need is a place where you can crouch down, and you can't be stood in deep water. In this crafting section, you can also modify your currently equipped melee weapon to make it more deadly temporarily. Melee weapons all have a limited amount of hits attached to them, so you will need to pick up a new one regularly. On the other hand, rifles and handguns don't degrade, but you will of course run out of bullets so you need to be very careful when you decide to use your guns.
The majority of this game can be played stealthily, but there are times where you have no choice but to out and out attack. This is when things get crazy. If you hadn't prepared beforehand and created bombs and health packs for example, you will really find these situations difficult to survive. You can also collect salvage parts throughout the game, and upgrade your projectile weapons at a workbench. There is also a third upgrade menu where you can upgrade Joel's abilities, such as maximum health, listening distance and more. And if that wasn't enough, there is one more way to upgrade your abilities; picking up special training manuals, which makes you want to look everywhere even more.