It also farts a lot
Unlike most things we pop into the oven, yeast enters while it’s still alive. Luckily it’s very tiny and can’t fight back. Why are we so sadistic as to roast these poor defenseless little beings as they still live and breathe, when we give most other foods the courtesy of dying first? Because we’re dependent on yeast to live fast and die young to create scrumptious breads and baked goods. We slip them into warm baths, ply them with sugar (their favorite) to get all loosey goosey, and let them party like madmen for a few hours before we burn them alive.
During this time—a veritable yeasty bacchanalia—they can’t stop eating and, as normally accompanies such gluttony, they also cannot stop farting. Those delectable farts are what makes dough rise. If you didn’t know this flatulent factoid before today, you’re welcome.
The first instruction given in most bread recipes is to “bloom” the yeast: mix with some warm water and sugar, let it sit for about 10 minutes until foamy. That’s a hell of a lot of waiting around, and you didn’t get to baking because you wanted to sit around staring at a bowl for ten minutes. So is it necessary? From a technical standpoint, no. From a “preserving your sanity and not wasting everyone's time” standpoint, yes.
The blooming process is when you “wake up” the yeast from its dehydrated state of suspended animation. The warm water will revive it, and the sugar will feed it so it can begin farting with glee the second it regains consciousness. It’s worth bothering with the wait because you want to be sure beyond the shadow of a doubt that your yeast is alive and raring to go. If the water you mix the yeast with is too hot it will die immediately, and you’ll never know if you’ve made this mistake if you dive headfirst into step two. If the water is too cold, it will never wake up, and you’ll just have sleepy, starving yeast rolling around in your dough.
Your water temperature ideally needs to be between 105-115 degrees, and if you don’t have a thermometer this can be a highly stressful situation. Don’t bother bringing the stove or microwave into this; it’s an unnecessary step that will almost always result in water that’s too hot. Instead, run water from the tap until it feels just warm to the inside of your wrist. Stir well with the sugar and yeast, then go off to measure out the rest of your ingredients.
If it’s bubbly and smelly by the time you return, then rock on with your bad self. If it’s nothing but a stagnant beige puddle, toss and try again. You cannot save it, and it will do nothing for you going forward except destroy all your hard work. Take the extra step. Go forward with confidence. The journey to a hot loaf of bread should never end with disappointment.