A digital footprint is the information that is visible/ left behind by a user online as a result of their input.
Whether you have just met somebody, applied for a job or are 'that' employee that gets the same bus on a morning, you can count on being Googled. Employers nowadays do Google potential candidates when recruiting, so make sure what's online about you is suitable for an employer. Before making yourself aware to an employer using any form of social media, you need to be aware of your digital footprint. You have control of your digital identity and should take advantage of this to make a positive impression.
Here’s a few pointers to get you started: