Lets start by saying out loud, “COMPUTERS AREN’T PERFECT, THEY BREAK”. Seriously you could get anything from a corrupt file, to a virus, to hardware issues (motherboard, power supply, hard drive could fail). If you are walking with a laptop or a tablet, you could trip, drop it and have it break (Seriously that happens everyday). Having a good and valid backup can save you, at a minimum, your time and a major headache. Sometimes things on a computer are just irreplaceable. I guess your going to have to take the entire family on vacation back to Florida (or insert the location of your last vacation here), or you will have to ask your son/daughter to recreate their 1st baby steps (which will be awkward if they are now teenagers).
There are many ways to back up a computer. Files can be manually transferred to a storage device such as an external hard drive, or uploaded to an online storage facility. Files can be backed up individually or as an entire system. Software for performing backups can be downloaded for free or a very low-cost, may be part of a software suite, or included with a hardware backup utility. The option that will work best for you will depend on your needs and the importance of your files.