Whats a Bug out bag?
Imagine there's a natural disaster like an earthquake or a fire and you need to leave the house for some time or permanently, but you need to leave quickly! You'll not have the time to gather up your essential belongings.
The concept of a 'Bug-Out-Bag' is that you store important things (medication, first aid stuff, digital copies of your passport and other important files on USB sticks, money, a flashlight, a multitool, a charging cable for your smartphone or even a second smartphone, maybe emergency food, some emergency clothes) in a big backpack. When the shit hits the fan, you take your phone, your purse, your Bug-Out-Bag and you are ready to go. So you can leave the house in under a minute if need be.
Of course, if you store food and medicine, you need to check the expiration date and exchange those things if necessary. Having said that, there are emergency meals that last up to 25 years or even longer.