One of the driving ideas in Survival is the “ First Night .” While we have 24 hours for a spin around our axis, Minecraft is slimmed down to a 40 minute cycle (20 day and 20 night). It’s easy to get side-tracked when you start out: seeing what’s over that next hill, trying to find the perfect spot for your project, figuring out how to get out of that hole you just fell into... But you’re on a 20-minute countdown till dusk, and with dusk comes danger. It’s plenty of time for you to build a shelter, or build some weapons to protect yourself, or possibly even find a village that will shelter you- but in the back of your mind on day one should always be- night is coming, where am I going to going to be safe tonight?
If you’re interested in a survival walk-through there’s in-depth information on the Minecraft wiki: https://minecraft.gamepedia.com/Tutorials/Beginner%27s_guide .